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Petroleum Experts

PVTP

Version 6.5

October, 2003

USER GUIDE

The information in this document is subject to change as major improvements and/or amendments to the program are generated. When necessary, Petroleum Experts will issue the proper documentation. The software described in this manual is furnished under a licence agreement. The software may be used or copied only in accordance with the terms of the agreement. It is against the law to copy the software on any medium except as specifically allowed in the license agreement. No part of this documentation may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or information storage and retrieval systems for any purpose other than the purchaser's personal use, unless express written consent has been given by Petroleum Experts Limited. All names of companies, wells, persons or products contained in this documentation are part of a fictitious scenario or scenarios and are used solely to document the use of a Petroleum Experts product. Address: Registered Office: Petroleum Experts Limited Petroleum Experts Limited Spectrum House Spectrum House 2 Powderhall Road 2 Powderhall Road Edinburgh, Scotland Edinburgh, Scotland EH7 4GB EH7 4GB Tel: (44 131) 474 7030 Fax: (44 131) 474 7031 Email: [email protected] Internet: www.petroleumexperts.com

PVTP

1 Introduction..................................................................................................................................1

1.1 PVT provides...........................................................................................................................1 2 Installation and Windows Basics ..............................................................................................1

2.1 Software and Hardware Requirements ...................................................................................1 2.1.1 Upgrading from a Previous Version ..............................................................................3

2.2 Installing PVTP........................................................................................................................3

2.2.1 Running Setup...............................................................................................................4 2.2.2 The PROSPER.INI file ..................................................................................................4

2.3 Starting PVTP..........................................................................................................................5

2.3.1 Connecting The Software Protection Bitlock.................................................................5 2.3.2 Creating the PVTP Icon.................................................................................................5

2.4 REMOTE Software Utility ........................................................................................................6

2.4.1 Entering the User Authorisation Code...........................................................................6 2.4.2 Updating the Software Protection Bitlock......................................................................8

2.5 Program Check List.................................................................................................................8

3 File Management .........................................................................................................................1

3.1 PVT File Types........................................................................................................................1 3.2 PVT Data Files ........................................................................................................................2

3.2.1 PVT Project File (*.PVI ) ................................................................................................2 3.2.2 Extract Data (*.PVI) .......................................................................................................2 3.2.3 PVT Import ....................................................................................................................2 3.2.4 PVT Export Files............................................................................................................4 3.2.5 PROSPER EoS Composition (*.PRP)..........................................................................4 3.2.6 PROSPER Hydrate Formation (*.PHY).........................................................................5 3.2.7 General Data Export (*.PVE)........................................................................................5 3.2.8 Black Oil Tables (*.PTB)................................................................................................8 3.2.9 MBAL MultiI-PVT Export (*.PGD)................................................................................13 3.2.10 MBAL PVT with Depth - Black Oil Match Tables ........................................................16 3.2.11 MBAL Variable Bubble Point(Oil) Export (*.PVB)........................................................20 3.2.12 Saturated .....................................................................................................................20 3.2.13 Undersaturated............................................................................................................20

3.3 MBAL Variable Bpt. Calculation Dialog.................................................................................25

3.3.1 Eclipse Type Export (*.INC) ........................................................................................29 3.3.2 Eclipse Export Setup Dialog.......................................................................................30 3.3.3 Eclipse Export Tables..................................................................................................34 3.3.4 Eclipse Compositional Export (*.PVO) .......................................................................37 3.3.5 PVT Temporary Files ..................................................................................................38

3.3.5.1 Temporary Data File (*.PSV)...............................................................................38 3.4 File Operations ......................................................................................................................38

3.4.1 Creating a New File.....................................................................................................38 3.4.2 Opening an Existing File .............................................................................................38 3.4.3 Saving a File................................................................................................................39 3.4.4 Copying a File..............................................................................................................39 3.4.5 Closing Files ................................................................................................................39 3.4.6 Restore Temp File .......................................................................................................39

3.5 Software Key Maintenance ...................................................................................................40

3.5.1 Viewing the Software Key ...........................................................................................40

PETROLEUM EXPERTS LTD

PVTP

3.6 Printing ..................................................................................................................................40

3.6.1 Printer Set-up ..............................................................................................................40 3.6.2 Printing a Report..........................................................................................................41

3.7 Units System .........................................................................................................................42

3.7.1 Unit Options.................................................................................................................42 3.7.2 Variables......................................................................................................................42 3.7.3 Validation.....................................................................................................................43 3.7.4 Unit Systems ...............................................................................................................43 3.7.5 Changing the Units ......................................................................................................43 3.7.6 Validation Limits ..........................................................................................................43

3.8 Command Buttons.................................................................................................................44

4 Models and Model Options.........................................................................................................1

4.1 The Black Oil Model ................................................................................................................1 4.2 The Equation of State Model...................................................................................................1

4.2.1 The Acentric Factor .......................................................................................................2 4.2.2 The Binary Interaction Coefficient .................................................................................6 4.2.3 Volume Shift ..................................................................................................................8 4.2.3.1 Volume Shift Setup........................................................................................................9

4.3 Wax Modelling.......................................................................................................................12

4.3.1 Wax Model Details.......................................................................................................15 4.3.2 Wax Model References ...............................................................................................18

4.4 Hydrates ................................................................................................................................19

4.4.1 Background to Hydrates..............................................................................................19 4.4.2 Hydrate Modelling........................................................................................................21 4.4.3 Hydrate Inhibition.........................................................................................................23 4.4.4 Hydrate Model References..........................................................................................24

4.5 Compositional Gradient.........................................................................................................25

4.5.1 Background to Compositional Gradient ......................................................................25 4.5.2 Compositional Gradient References ...........................................................................28

4.6 Viscosity and Thermal Conductivity Models..........................................................................29

4.6.1 Lohrenz,Bray,ClarkViscosity Model.............................................................................30 4.6.2 Pedersen et al Viscosity Model ...................................................................................31 4.6.3 Zhou et al Viscosity Model ..........................................................................................32 4.6.4 Little and Kennedy Viscosity Model.............................................................................34 4.6.5 Thermal Conductivity Model........................................................................................35 4.6.6 Viscosity and Thermal Conductivity References.........................................................36

4.7 Water Modelling ....................................................................................................................38

4.7.1 Water Modelling References .......................................................................................39


PVTP

5 Main/Stream Options ..................................................................................................................1

5.1 PVT Main Menu.......................................................................................................................1 5.1.1 File.................................................................................................................................2 5.1.2 Options ..........................................................................................................................2 5.1.3 Data ...............................................................................................................................2 5.1.4 Calculation.....................................................................................................................2 5.1.5 Calc. Solids....................................................................................................................2 5.1.6 Streams .........................................................................................................................2 5.1.7 Reporting .......................................................................................................................2 5.1.8 Utilities ...........................................................................................................................2 5.1.9 Preferences ...................................................................................................................3 5.1.10 Window..........................................................................................................................3

5.2 Toolbar ....................................................................................................................................3 5.3 Summary Page........................................................................................................................6 5.4 Option Selection ......................................................................................................................8

5.4.1 Option Selection ............................................................................................................8 5.4.2 PVT Method...................................................................................................................8 5.4.3 Fluid Type......................................................................................................................9 5.4.4 Separator.......................................................................................................................9 5.4.5 Equation of State...........................................................................................................9 5.4.6 User Information............................................................................................................9 5.4.7 User Comments...........................................................................................................10

5.5 Streams Menu .......................................................................................................................10

5.5.1 Edit Stream Details......................................................................................................11 5.5.2 Add Stream..................................................................................................................11 5.5.3 Delete Stream..............................................................................................................14 5.5.4 Create a Stream to a target GOR................................................................................15 5.5.5 Create a Stream to a target Saturation Pressure........................................................16 5.5.6 Blend Streams.............................................................................................................18 5.5.7 Allocate:Blend Streams to a Target GOR ...................................................................19 5.5.8 Add Water : Create a Stream with a Fixed Amount of Water .....................................21 5.5.9 Add Water : Create a Stream Saturated with Water ...................................................22


PVTP

6 Black Oil Input .............................................................................................................................1

6.1 BLACK OIL PVT - General......................................................................................................1 6.2 Toolbar ....................................................................................................................................2

6.2.1 BLACK OIL PVT - Oil ....................................................................................................3 6.2.2 Match Data ....................................................................................................................3 6.2.3 Regression ....................................................................................................................4 6.2.4 Match.............................................................................................................................4 6.2.5 Match-all ........................................................................................................................4 6.2.6 Parameters ....................................................................................................................5 6.2.7 Viewing the Match Parameters .....................................................................................5 6.2.8 Calculations ...................................................................................................................5 6.2.9 Calculating PVT Data ....................................................................................................6 6.2.10 Plotting the Calculated Data..........................................................................................7 6.2.11 BLACK OIL PVT - Dry and Wet Gas.............................................................................8

6.2.11.1 Input Data ..............................................................................................................8 6.2.11.2 Match Data ............................................................................................................8

6.2.12 BLACK OIL PVT - Retrograde Condensate ..................................................................9 6.2.12.1 Input Data ..............................................................................................................9 6.2.12.2 Match Data ............................................................................................................9

7 Input Data EoS.............................................................................................................................1

7.1 General Project Data Structure ...............................................................................................1 7.1.1 STREAMS .....................................................................................................................1 7.1.2 PSEUDO STORAGE.....................................................................................................2

7.2 Selecting Components ............................................................................................................3

7.2.1 User Database Entries ..................................................................................................4 7.2.2 Recombination...............................................................................................................5

7.2.2.1 MODE....................................................................................................................5 7.3 Edit Composition .....................................................................................................................9 7.4 Pseudo Properties.................................................................................................................14

7.4.1 Auto Matching of Densities..........................................................................................15 7.4.2 Automatic Mode...........................................................................................................16 7.4.3 Manual Mode...............................................................................................................17 7.4.4 Hint on Method ............................................................................................................17 7.4.5 Auto-Matching of Densities and Viscosities ................................................................19 7.4.6 AutoMatching Viscosities ............................................................................................20 7.4.7 Splitting/Profilling Last Pseudo....................................................................................20 7.4.8 Original Numbers Store...............................................................................................22 7.4.9 Advanced Splitting Dialog ...........................................................................................22 7.4.10 Split Profiles.................................................................................................................23 7.4.11 COPYING A SPLIT......................................................................................................26 7.4.12 Split Profile Dialog .......................................................................................................26 7.4.13 COPYING A PROFILE ................................................................................................28

7.5 Binary Interaction Coefficients...............................................................................................29 7.6 Grouping and Properties Information ....................................................................................30

7.6.1 Control Buttons............................................................................................................32 7.6.2 OmegaA and OmegaB ................................................................................................34 7.6.3 Plotting Component Properties ...................................................................................36

7.7 Grouping................................................................................................................................37 7.8 Reference Data .....................................................................................................................39


PVTP

7.9 Decontamination ...................................................................................................................40

7.9.1 Edit Mole Percents ......................................................................................................40 7.9.2 Decontamination Control Dialog..................................................................................41

7.9.2.1 Decontamination Mode Selection Dialog ............................................................44 7.9.2.2 Decontamination Quick Look Dialog ...................................................................44 7.9.2.3 Decontamination Pseudos Dialog .......................................................................46

7.10 Match Data ............................................................................................................................47

7.10.1 Matching on Mixture Critical Temperature ..................................................................50 7.11 Regression ............................................................................................................................52

7.11.1 Regression Parameter Selection Dialog .....................................................................55 7.11.2 Volume Shift ................................................................................................................57 7.11.3 Control Buttons............................................................................................................57 7.11.4 Mouse Shortcuts..........................................................................................................58 7.11.5 Separator.....................................................................................................................58 7.11.6 What Properties to Use in Regression ........................................................................59 7.11.7 Matching Viscosity.......................................................................................................59 7.11.8 Regression With Solids ...............................................................................................63 7.11.9 Model Selection...........................................................................................................65 7.11.10 Notes on Regression...................................................................................................65 7.11.11 Regression with OmegaA and OmegaB .....................................................................66

7.12 Plot Test Points .....................................................................................................................67

8 Calculation EoS ...........................................................................................................................1

8.1 Critical Point Calculation .........................................................................................................2 8.2 Phase Envelope ......................................................................................................................3 8.3 Ranged Saturation Pressure...................................................................................................7 8.4 Constant Composition Expansion (CCE) ................................................................................9

8.4.1 The Calculation Display...............................................................................................13 8.4.2 The Analysis Display ...................................................................................................15 8.4.3 The Copy to Clipboard Dialog .....................................................................................17

8.5 Constant Volume Depletion(CVD) ........................................................................................18 8.6 Depletion Study(DEPL) .........................................................................................................21 8.7 Differential Expansion(DIFF) .................................................................................................24 8.8 Composite Differential Expansion(COMPOS).......................................................................27 8.9 Separator Process.................................................................................................................29 8.10 Compositional Gradient.........................................................................................................34

8.10.1 Calculation Results Display.........................................................................................38 8.11 Swelling Test .........................................................................................................................39 8.12 Slim-tube Simulation .............................................................................................................41

8.12.1 Slim-tube Input dialog..................................................................................................42 8.12.2 Slim-tube cell data dialog ............................................................................................46 8.12.3 Slim-tube cell data dialog ............................................................................................47 8.12.4 Slim-tube time steps dialog .........................................................................................48 8.12.5 Slim-tube calculations dialog.......................................................................................49


PVTP

8.12.6 Slim-tube analysis dialog.............................................................................................51 8.12.7 Slim-tube cell detail dialog...........................................................................................52

8.13 Quick Calculation Control Button ..........................................................................................53

8.13.1 Small Separator Calculation Dialog.............................................................................55 9 Calculation of Solids...................................................................................................................1

9.1 Wax Amount Calculation .........................................................................................................1 9.1.1 The Analysis Display .....................................................................................................4

9.2 Wax Appearance Temperature ...............................................................................................5 9.3 Hydrate Formation Pressure ...................................................................................................8

9.3.1 Calculations Dialog......................................................................................................12 9.4 Hydrate Minimum Inhibitor Concentration.............................................................................12

10 Reporting......................................................................................................................................1

10.1 Setting Up the Reporting System............................................................................................1 10.2 Reports ....................................................................................................................................1 10.3 Template Editor Commands....................................................................................................4

11 Plotting 1

11.1 The Plot Display ......................................................................................................................1 11.1.1 Manipulating Streams....................................................................................................1 11.1.2 Manipulating Curves......................................................................................................2 11.1.3 The Plot Menu and Toolbar...........................................................................................5

11.2 Plot Menu Options...................................................................................................................7

11.2.1 File.................................................................................................................................7 11.2.2 Display...........................................................................................................................8 11.2.3 Output............................................................................................................................9

11.3 The Toolbar Options..............................................................................................................10

12 Utilities 1

12.1 API/Density Calculator ............................................................................................................1 12.2 Mass Balance Calculator.........................................................................................................2 12.3 Enthalpy Balance Calculator ...................................................................................................4

12.3.1 Single Point Enthalpy Balance ......................................................................................4 12.3.2 Multiple Point Enthalpy Balance....................................................................................5

12.4 Hoffmann Quality Plot .............................................................................................................7

13 User Databases ...........................................................................................................................1

13.1 Creating a User Database.......................................................................................................2 13.2 Selecting a User Database Directory ......................................................................................3 13.3 Editing a User Database .........................................................................................................4


PVTP

13.4 Importing into User Database..................................................................................................6 14 Preferences..................................................................................................................................1

14.1 Adjusting the Equation of State Calculation Tolerences .........................................................2 Appendix A - Worked Examples .......................................................................................................1

A1 Example 1 - EOS calibration of oil sample using PVTP..........................................................1 A1.1 Step-by-step approach to building an EOS model in PVTP..........................................3 A1.2 Step-by-step approach to Calibrating an EOS model in PVTP...................................14 A1.3 Using PVTP to generate Tables for other applications ...............................................23

A2 Example 2 - EOS calibration of a Condensate Sample using PVTP ....................................30

A2.1 Step-by-step approach to building an EOS model in PVTP........................................33 A2.2 Calibrating an the EOS model in PVTP ......................................................................37 A2.3 Checking results of the calibrated model against lab data..........................................40 A2.4 Simulating PVT Experiments in PVTP ........................................................................42

A3 Example 3 – Estimating Decontaminated sample properties of an contaminated Oil Sample using PVTP......................................................................................................................................47

A3.1 Step-by-step approach to decontamination in PVTP ..................................................50 Appendix B Step by Step Guide .......................................................................................................1

B1 List of Steps.............................................................................................................................1 B1.1 Step 1: Create a New File .............................................................................................2 B1.2 Step 2: Select Equation of State Options......................................................................3 B1.3 Step 3: Select Components...........................................................................................4 B1.4 Step 4: Enter Composition ............................................................................................6

B2 Sample PVT Report Composition ...........................................................................................8

B2.1 Step 5: Initialise the Pseudo Component Properties.....................................................9 B2.2 Step 6: Match the Surface Volumetric Properties (Density, GOR etc.) using the Automatch feature .......................................................................................................................11 B2.3 Step 7: Use Pseudo-Splitting or BI Coefficients to get near Reservoir Saturation Pressure Value............................................................................................................................13

B2.3.1 Strategy for Achieving Saturation Pressure ........................................................15 B2.3.2 Using BI Coefficients ...........................................................................................18 B2.3.3 Using Pseudo Splitting ........................................................................................20

B2.4 Step 8: Select Match Parameters................................................................................22 B2.4.1 How is Match Data entered? ...............................................................................23

B2.5 Step 9: Use Regression to Match Fluid.......................................................................27 B2.6 Step 10: Check and Refine the Fluid Characterisation ...............................................29 B2.7 Step 11: Calculate, Report and Export........................................................................30

Appendix C Decontamination Procedure ........................................................................................1


PVTP


Appendix D PVTP OPEN SERVER Manual...........................................................................................1

D1 Introduction..............................................................................................................................1 D1.1 About This Guide...........................................................................................................1 D1.2 What is in this guide ......................................................................................................1 D1.3 How To Use This Guide ................................................................................................2 D1.4 Symbols and Conventions.............................................................................................2

D2 Overview..................................................................................................................................3

D2.1 Basic Functions .............................................................................................................3 D2.2 GetValue........................................................................................................................3 D2.3 SetValue ........................................................................................................................3 D2.4 DoCommand .................................................................................................................3 D2.5 Calling the Functions.....................................................................................................4 D2.6 Automation ....................................................................................................................4 D2.7 Batch File.......................................................................................................................4

D3 Potential Uses .........................................................................................................................5

D3.1 Batch Runs ....................................................................................................................5 D3.2 Custom Reporting..........................................................................................................5 D3.3 Data Import/Export ........................................................................................................6 D3.4 Enhanced Prediction Runs in GAP ...............................................................................6 D3.5 Running PETEX programs with other engineering software applications.....................6

D4 Support ....................................................................................................................................7 D5 Using the OPENSERVER ...........................................................................................................8

D5.1 Variable Text Strings .....................................................................................................8 D5.2 Automation ....................................................................................................................9

D5.2.1 Example Macro....................................................................................................10 D5.2.2 Framework...........................................................................................................11 D5.2.3 DoCommand .......................................................................................................12 D5.2.4 SetValue ..............................................................................................................12 D5.2.5 DoCommandAsync..............................................................................................13 D5.2.6 GetValue..............................................................................................................13

D5.3 Batch File.....................................................................................................................15 D5.3.1 Running a Batch File ...........................................................................................15 D5.3.2 Formatting Commands........................................................................................16 D5.3.3 DoCommand .......................................................................................................16 D5.3.4 SetValue ..............................................................................................................16 D5.3.5 GetValue and GetValPrint ...................................................................................17

D6 PVTP and the OPENSERVER..................................................................................................18

D6.1 OverView .....................................................................................................................18 D6.2 File and Streams .........................................................................................................19 D6.3 BLACKOIL ...................................................................................................................20 D6.4 OPTIONS ....................................................................................................................21 D6.5 STREAMBASE[stream no. or stream name] ..............................................................22 D6.6 STREAMRUN[stream no. or stream name] ................................................................25 D6.7 CALCUL[stream no. or stream name].........................................................................27 D6.8 Carrying out Calculations and Obtaining Results........................................................31

D6.8.1 Analysis ...............................................................................................................33 D6.9 Flash Calculation.........................................................................................................34 D6.10 Small Separator Calculation........................................................................................34 D6.11 Saturation Pressure at Reference Calculation ............................................................36 D6.12 Recombination Calculations........................................................................................36 D6.13 Allocate: Blending to a target GOR .............................................................................37

1 Introduction Welcome to PVTP, Petroleum Experts Limited's advanced Pressure Volume and Temperature analysis software. PVT can assist the production or reservoir engineer predict the effect of process conditions on the composition of hydrocarbon mixtures with accuracy and speed. The compositional behaviour of complex mixtures including gas mixtures, gas condensates, retrograde condensates, volatile oils and black oils can be interpreted and predicted with confidence. The PVT package can be used as a stand-alone analytical tool, or can be used to

2 -3 PVTP User Guide

◊ Input of Binary Interraction Coefficients using a variety of correlations. ◊ Automatic or manual component grouping

• Calculation and graphical display of Phase Envelopes for a user-selectable range of vapour fractions

• Calculation of Saturation Pressure for complex mixtures at a single reference presure or over a range of entered pressures

• Prediction of compositional changes based on the following

◊ Contant Composition Expansion ◊ Constant Volume Depletion ◊ Depletion Study ◊ Differential Expansion ◊ Composite Differential Expansion

• Full Lab Data Matching including the following options

◊ Match with all component Tcs, Pcs,Afs etc. ◊ Match using a global Omega A and Omega B ◊ Match using individual component Omega A and Omega B values ◊ Limiting on match property movement ◊ Matching on mixture critical temperature

• Prediction of the formation of Solids

◊ Wax Amount ◊ Wax Appearance Temperature ◊ Hydrate Formation Pressure ◊ Hydrate Minimum Inhibitor Concentration

• A series of Utilities which

◊ Convert between API and Density ◊ Perfom a Material Balance to Validate PVT Report Data ◊ Perform a single and multiple point enthalpy balance calculation ◊ Perform a Hoffman-type Quality Plot

• Prediction of Separator liquid and gas compositions over a wide range of process conditions and feedstock compositions

• Prediction of composition changes with depth (composition gradient). Export of gradient results to multi-pvt MBAL

• Eclipse Format Export (Black Oil and Compositional)

PETROLEUM EXPERTS

CHAPTER 1 - INTRODUCTION 3 -3

PVTP User Guide

• Export and Import of Petroleum Experts standard *.prp format

• Swelling Tests with a second stream

• Slim-tube simulation

• Creation of a Stream to a Target GOR

• Creation of a Stream to a Target Saturation Pressure

• Alllocation of two streams to a target GOR Measurement Units A flexible system of units is provided. Data may be input using one set of units and output using a second set of units. Reporting The PVT package provides a full range of user-configurable reports for Input data and calculation results. Printing can be done in a range of fonts to any WINDOWS supported printer

2 Installation and Windows Basics

This chapter explains how to install PVTP on your computer. The guide assumes you have a working knowledge of Windows terms and procedures. If you are unfamiliar with the Windows operating system, we recommend you read the relevant sections in the Microsoft Windows User's Guide to learn more about Windows operations. This chapter gives instructions on installing the program to a Windows 98, 2000 or Windows NT operating system. 2.1 Software and Hardware Requirements The program supports all Windows-certified device drivers that are shipped with Windows. The list of devices, software and hardware supported by Windows is included with the documentation of your copy of Windows. PVTP can be run as single User licence or on a Network. In either case, a special security key is needed. The security key is called Bitlock for stand-alone licences and Hardlock for network licences The security key is provided by Petroleum Experts. The minimum requirement recommended for PVTP is Pentium 450 MHz machine with 128 Mbytes. In order to install the software from the CD, the machine should have access to a CD drive. For a stand-alone licence, a security key (Bitlock) provided by Petroleum Experts must be attached to the parallel printer port of the PC before PVTP can be run. For network installation, the security key (Hardlock) can be attached to any PC communicating with the network. You should refer to the separate installation procedure for network Hardlock sent with the purchase of a Hardlock licence. If PVTP has been installed for the first time on a machine, the Bitlock driver must be installed on this machine in order to establish the link between the software and the security key (Bitlock driver). In order to install the Bitlock driver, you will have to start from the main Windows screen. Here you click on |Start |Programs |Petroleum Experts IPM |Utilities and then start the “Set-up Bitlock Driver”.

2 - 8 PVTP User Guide

This will prompt the following screen.

From the screen above, you will have to run the |Functions |Install Sentinel Driver | OK. You might need to modify the path of the sentinel files. You should ensure that you have the permission to install a driver. Your IT manager can help you getting the required permission.

Petroleum Experts

Chapter 2 - Installation and Windows Basics 3 - 8

2.1.1 Upgrading from a Previous Version For convenience in running linked models, Petroleum Experts software products now installs by default into a common sub-directory \Program Files \Petroleum Experts\IPM X.Y. If you wish to keep an original version of the program, back it up into another directory before installing the upgrade.

All program upgrades are backward compatible. This ensures that data files created with earlier versions of the program can still be read by later program versions. However, if you save a data file with the new version, that file can no longer be opened by earlier versions! As with all new software installations, always back up your PVTP files.

2.2 Installing PVTP Before installing the program on your computer, you should first determine:

The drive where the program is to be installed • • •

• • •

• •

The amount of space available on the selected drive When installing on a network, verify you have the necessary access rights to create directories and files on the designated volume.

What Set-up does The installation procedure:

Creates a program directory on your hard disk. Creates a sample files sub directory on your hard disk. Unpacks the PVTP program and related files to the selected drive and directory. Creates a program initialisation file PROSPER.INI in your Windows directory. Creates a new Windows program group and icon for both PVTP and REMOTE.

If you are updating PVTP, the set-up can be used to modify, repair or remove components of the IPM suite. In this case, follow the online instructions

To avoid potential system resources conflicts, please shut down other applications before running SETUP. Some anti-Virus programs can interfere with the installation process and may need to be shut down.

PVTP User Guide


2.2.1 Running Setup To install the PVTP program:

1. Insert the program installation CD in the correct drive. 2. From the main screen of Windows, click on |Start |Run and follow the

online instructions.

The option “Repair” is recommended. 2.2.2 The PROSPER.INI file The PROSPER initialisation file contains the settings you use to customise the PVTP application environment. Settings such as the program data directory, customised units system, last file accessed and the colour settings of your screen graphics are all stored in this file. You do not need to manually modify the PROSPER.INI file. The program will automatically record any changes to the settings. PVTP automatically creates the PROSPER.INI file in the Windows default directory using the program's default settings. The location of this file is defined by this entry in your WIN.INI file:

[PETROLEUM EXPERTS] IniPath=PROSPER.INI

We do not recommend changing the location of the PROSPER.INI file. If however, you want to do so for specific reasons (to place it on a specific network drive), take the following steps:

1. First copy the existing PROSPER.INI file to the required directory. For example:

COPY C:\WINDOWS\PROSPER.INI U:\NETWORK\APPS\PVTP\PROSPER.INI

2. Next amend the 'IniPath' entry in WIN.INI to correspond to the new directory and path where the PROSPER.INI is now located. e.g.:

IniPath=U:\NETWORK\APPS\PVTP\PROSPER.INI

During the installation PVTP unpacks a number of files onto your computer in the specified installation directory. The unpacked files should not be modified, removed or moved to another directory.

Petroleum Experts


2.3 Starting PVTP Before starting the program, make sure the software protection Bitlock (dongle) is connected to your PC and that the Bitlock Driver has been installed. 2.3.1 Connecting The Software Protection Bitlock The software protection Bitlock must be attached to the PARALLEL printer port. Do Not connect the Bitlock to a serial port, as this can damage the Bitlock or your PC. If you are using protection Bitlocks for other software, we do not recommend stacking the Bitlocks. We suggest using only the correct Bitlock with the appropriate software. Stacking Bitlocks may lead to incompatibilities between Bitlocks, and may cause read/write or access errors with some Bitlocks. 2.3.2 Creating the PVTP Icon

The PVTP icon should appear automatically in the correct folder under the Programs menu after installation. If this does not happen, invoke the Start menu and select Settings | Taskbar. Select the Start Menu Programs tab and click on Add to add the PVTP program to the menu. Follow the instructions on the screen. To start the program subsequently, select the PVTP program from the programs menu of the Start menu. It is also possible to create a shortcut to PVTP on the main Windows desktop. To do this, click the right hand mouse button anywhere within the desktop and select New | Shortcut from the resulting popup menu. Follow the instructions on the screen to create the shortcut to PVTP.EXE. PVTP can then be executed by double-clicking on the shortcut icon.

PVTP User Guide


2.4 REMOTE Software Utility All Petroleum Experts' software requires a software protection device to allow it run. The utility program REMOTE.EXE provided with our software allows you to access the software protection device to view information such as the enabled program options, program expiry date(s), and Bitlock number. You may have been sent an inactive software device. For security, authorisation codes are always sent separately to the Bitlock. On receiving the software package, we ask that you contact us to confirm reception. We will then verify the user access code programmed on your Bitlock, and issue a set of codes to activate the Bitlock. In these situations, the necessary codes will be sent to you by facsimile, letter or email. To enter the codes, you will need to run the REMOTE application installed with PVTP (see next section for more details). You can also create a shortcut to the Remote application from the Windows desktop. For this, click on |New |Short cut anywhere on the Windows screen and follow the online instruction. The program file is called REMOTE.EXE. 2.4.1 Entering the User Authorisation Code You enter user authorisation codes only if:

The software protection Bitlock you have received is inactive, • • •

Access period for the program has expired, or You have acquired new program options

To enter authorisation codes take the following steps:

Double click the REMOTE icon (or select the REMOTE program from thePrograms menu of Windows 98). A screen similar to the following will appear:

Petroleum Experts


Figure 2.1: REMOTE SoftwareBitlock Utility

If your software protection Bitlock is already active, a list of enabled programs will appear in the Remote screen as above. If PVTP has already been enabled, no further action is needed. If this is the case, exit the Remote Utility program now. No user authorisation code is required.

If the code has expired or has not been enabled, the Bitlock should be activated with the set of codes provided by Petroleum Experts. To do so, you click on the |Update button on the bottom of the previous screen and the following screen will appear:

Figure 2.2: Authorisation Codes Entryscreen

Enter the codes from Left to Right beginning with the top row (you may use <Tab> to move between the items). Press |Continue to activate the codes. You will then be returned to the 'Remote Software Bitlock Utility' screen. If you have received authorisation codes for more than one program, click 'Update Software Bitlock' again, and enter the codes for the next program.

PVTP User Guide


Petroleum Experts

2.4.2 Updating the Software Protection Bitlock Access to the software ceases automatically when the license expiry date elapses. You are, however, reminded several days in advance. This gives you sufficient time to contact Petroleum Experts about new codes. Software Bitlocks require updating when: • •

The software license period has ended. The annual maintenance fee is due.

Software protection Bitlocks also needs updating when you acquire other Petroleum Experts software packages. The procedure to update the Bitlock is the same as for entering the authorisation codes. When the appropriate screen appears, enter the codes provided - from left to right beginning with the top row. Press OK to activate the codes, or Cancel to quit the update. To view the expiry date for any of the listed programs, simply click (highlight) the software name.

Perpetual licence holders will be sent on yearly basis an utility programwritten by Petroleum Experts, that automatically updates the Bitlock. Theupdate is hard-coded inside the utility program. step-by-step instructions aresent with this utility program.

2.5 Program Check List To ensure trouble free processing and access to the PVTP program, please check: •

•

•

•

•

•

You have sufficient disk space.

The software protection Bitlock is connected to your Parallel printer port. Do Not connect the Bitlock to the serial port, as this can damage the Bitlock or your PC.

The software protection Bitlock is firmly in place ensuring a good connection. If the Bitlock is loose the program may not be able to access the dongle to activate the program.

The printer cable is firmly attached to the software Bitlock. Your printer should be turned ON and be put on-line.

The PC system date is set correctly to the current date (i.e. today's date).

You back up your files on a regular basis with disk utility programs. This could help to avoid the corruption of files, or help detect potential problems with your hard disk before it is too late.

3 File Management This section describes the menus, options and procedures used in PVT to create new files and open or save existing files. The Units system and how to define printer settings and is outlined. The menus described in this section are the PVT File menu and Units menu. The File menu provides the ability to open , close , save etc. The PVT package allows multiple files to be opened at once. The Window Menu allows the user to swap between opened files. This menu offers the user the standard options available from an MDI (Multi Document Interface)

The PVT package can load multiple PVT Project Files each of which occupies its own window. The windows can be selected ,cascaded,arranged and tiled via this menu. Before you can work with a file, it must be opened. This can be done using the File menu Open option or the icon. To protect your work, you should save your data on a regular basis. Saving a file is done using the File menu Save or Save As options. This simple procedure could potentially prevent hours of work and analysis being lost. To start a new PVT Project file use the File menu New option. 3.1 PVT File Types PVT uses a flexible file structure that enables data to be easily exchanged between files and other application programs. In PVT, information is grouped into the following categories:

PVT Project File • • • • •

Import Export Temporary Report

and saved into the following types of data file:

3-2 PVPT User Guide

3.2 PVT Data Files 3.2.1 PVT Project File (*.PVI ) This is the main type of PVT package file . The information file contains all the composition input, matching and calculation data for multiple streams. When opened the main data points are shown within the main PVT window. 3.2.2 Extract Data (*.PVI) This file contains the results a particular set of calculations plus the composition which produced it. The file is produced using the Extract option within the Analysis window or from the View properties display. When opened the file behaves in the same way as the original PVI file from which the data was extracted 3.2.3 PVT Import This function is accessed by using the Import option from the File menu. The selection dialog is shown in figure 3.0. Figure 3.0: Import File Type Dialog

PVI File Import. This imports a stream from another PVTP *.PVI file. This option is explained in Streams - Adding a Stream (Chapter 5) ASCII File Import. Two ACII file options are available by selecting from the combo box and clicking on the Import from ASCII file: The types are 1. Importing a *.PRP file. This is the file type that is produced from the Proper compositional export and the various compositional and compositional areas in the other PETEX programs. This feature allows the user to take this file back inito PVTP and make a working stream with it. (see 3.1.4 Export PROSPER EoS for more details)

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Chapter 3 - File Management 3-3

2 Importing a *.EQL Data File A working example of an import file is contained within the PVT\SAMPLES directory with the file name example.eql. With time it is anticipated that there will be several import types to choose from . At present importing is limited to a text file with the following format : line 1 No Data Read line 2 No Data Read line 3 Number Of Components n (including Pseudos) <tab> Number Of Pseudo Components line 4 No Data Read line 4,6,.......2n+3 Component name eg. C1, CO2, C11+ (note only one name per line). See note below for names with * line 5,7......2n+4 Component properties in the following order separated by tabs i.e. mole % component <tab> Specific Gravity <tab> Boiling Point (deg C) <tab> Molecular Weight <tab> Critical Temperature (deg C) <tab> Critical Pressure (atm) <tab > Acentric Factor<tab> Critical Volume Note: These values ,other than mole % , are not required at present for pure components as they are overwritten by Petroleum Experts Database values. However, if you wish the values to remain , add the character * to the end of the name . Example C1* within EXAMPLE.EQL in the samples directory. All values are preferred for Pseudos. If no Boiling Point or SG is present (shown by 0.00 value), the missing numbers will be calculated. line 2n+5 No Data Read line 2n+6 No Data Read line 2n+7 .. end-1 Component Binary Interaction Coefficients in form: component x number <tab> component y number <tab> BI Coefficient value line end the end of data is marked by three 1000s separated by tabs Once the text file is imported via the file load dialog , the PVT file must be fully initialised by • Clicking on the Select Components option within the Data Menu then Clicking on OK • When the Composition Input Screen loads press Properties to bring up the Pseudo

Screen i.e if pseudos are required. • When the Pseudo Properties display loads , press OK to calculate any missing pseudo

values. • Press OK on the Composition Input Screen when it reappears to return to the main

display • Save the PVT file with the required name WARNING : if pseudo properties are not set up as described errors will occur eg. with density calculations

PVTP User Guide

3-4 PVPT User Guide

3.2.4 PVT Export Files 3.2.5 PROSPER EoS Composition (*.PRP) PRP files contain the data required by the PVT section of Petroleum Experts PROSPER program. The file is produced using the Export option within View properties display or by using the Export option from the File menu. Select Type 1 – PROSPER EoS Composition from the Export Types Dialog Screen (Figure 3.1) Figure 3.1: Export File Type Dialog

Only a limited subset of the data normally associated with a PVT file is required by PROSPER VIZ.

∗ Equation Type (SRK or Peng Robinson) ∗ Property Names and Units ∗ Composition (mole %) for each component ∗ Critical Temperature for each component ∗ Critical Pressure for each component ∗ Critical Volume for each component ∗ Acentric Factor for each component ∗ Molecular Weight for each component ∗ Specific Gravity for each component ∗ Volume Shift S Factor ∗ Parachor for each component ∗ OmegaA value for each component ∗ OmegaB value for each component ∗ Binary Interaction Coefficients for all component

combinations ∗ Separator Temperatures and Pressures are included if any have been used to correct fluid GOR and FVF.

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Note: All the values exported are in field units. 3.2.6 PROSPER Hydrate Formation (*.PHY) PHY files contain a table of temperatures and hydrate formation pressures. After calculation the export is available from the Calculation Results dialog or from the Export Type dialog. 3.2.7 General Data Export (*.PVE) PVE files are files produced by the PVT General Export Function. The ASCII text file is produced using the Export option within View properties display or using the Export Option from the File Menu Select Type 2 - Petex General from the Export Types Dialog Screen (figure 3.1) The Selection screens which follow give the user the choice of exporting any combination of :

∗ PVT Options ∗ Primary Input Composition and BI Coefficients. ∗ Grouped/Matched Composition and BI Coefficients. ∗ Reference Data ∗ Calculations ∗

The Calculation columns to be exported can be individually selected using the Column Setup dialog. The data exported can be delimited by tabs or commas or alternatively saved in a fixed-column-size format. Deselecting the saving of column headings and Keywords will produce a file containing only numeric data. If headings are required, a comment marker of your choice can be added to give the importing program a marker to search for. The General Export Display is shown in figure 3.2. Figure 3.2 Export File Dialog

PVTP User Guide

3-6 PVPT User Guide

The dialog gives the user great flexibility in what should be exported and in what format. The export is to an ASCII file with a default extension of .PVE For each section of Input Data or results a check-box allows the user to switch on or off its export . The available sections are: Input Data Included are all the entries made on the PVT Options screen i.e. Method, Analyst, Well etc. Input Composition This is component concentrations and properties of the mixture prior to any grouping or regression exported in tabular form. The currently selected Stream will be exported at this point. BI Coefficients. The initial values for Binary Interaction Coefficients are exported in a symmetrical table. Grouped/Matched Composition This is component concentrations and properties of the mixture after Grouping or Regression exported in tabular form. Grouped/Matched BI Coefficients. The Grouped/Matched values for Binary Interaction Coefficients are exported in a symmetrical table. Reference Data This option will export the Reference Temperature, Pressure and depth. Calculations When the dialog is loaded, the listbox within this section displays all the calculations which may be exported. A checkbox allows all calculation exporting to be switched on or off. Highlighted Calculation names will be exported. Clicking on the calculation name within the listbox will select or de-select the item. The variables within each calculation can be individually selected using the Layout option. Delimiting The data exported can be delimited by tabs or commas or alternatively saved in a fixed-column-size format. Enter the column width in the edit box if the fixed-column-size option is required. Headings and Comments Deselecting the saving of column headings and Keywords will produce a file containing only numeric data. If headings are required a comment marker of your choice can be added to give the importing program a marker to search for. Erasing the comment marker editbox contents will give headings without an added character. When all the selections have been made click on the Export control button to bring up the file save dialog. A file extension of .PVE is taken as default, but any legitimate file name can be used.

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Layout The Layout screen (shown in figure 3.3) is the same as used in all the calculations (chapter 8 ).Each selected calculation will be shown as a separate dilaogue within which individual values can be selected. Figure 3.3 Column Setup Dialog

To select or de-select a value click on the checkbox beside its name. To remove all selections for a particular calculation click on the Hide All button. To export all columns click on the All button above the listbox. When all column selections have been made click on OK . Clicking on Cancel will shut down the display , ignoring any selections which have been made.

PVTP User Guide

3-8 PVPT User Guide

3.2.8 Black Oil Tables (*.PTB) PTB files are files which contain the data in a form which can be imported into the PVT/BlackOil/Tables section of Petroleum Experts PROSPER program. The format is fairly general and could be used for other packages. An ASCII text file is produced by this procedure. The process is carried out using the Export option within View properties display or using the Export Option from the File Menu Select Type 3 -Black Oil Table from the Export Types Dialog Screen (figure 3.1) The Selection screens which follow give the user the choice of exporting any combination of the following Black Oil related variables:

∗ Pressure ∗ Gas to Oil Ratio(GOR) ∗ Oil FVF ∗ Oil Viscosity ∗ Oil Density ∗ Oil Z Factor ∗ Gas FVF ∗ Gas Viscosity ∗ Gas Z Factor ∗ Gas Density ∗ Condensate to Gas Ratio (CGR) ∗ Vapour CGR ∗ Water viscosity ∗ Water Z Factor

A typical dialog is shown in figure 1.2a. Note : The column values can be calculated for each pressure entry. If the Saturation Pressure is not included in the list within the table it is calculated and inserted when Export is selected. The varables to be exported are selected using the list box on the right of the display. At least one variable should be chosen. At the time of export the program checks if a selected table has any valid data for the chosen columns. If none exists the table is ignored. Selecting for MBAL/PROSPER

This feature has been added to assist in the transfer of the correct columns to MBAL's or PROSPER's table import facility. To use this option Select the target program using the combo box provided then select the type of fluid (defined in MBAL's or Proper's OPTIONS) using the radio

buttons finally click on the Select button. This automatically sets the required variables for

export.

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3-10 PVPT User Guide

Separator Data In common with the CCE calculation (Section 8.4) , the Table Export displays contains a section for Separator Data. This allows the user to define a 5-stage separator train through which the CCE liquid will be flashed to correct the Oil FVF and GOR. The processes which are used to return an oil to standard conditions can significantly change the final oil characteristics and the amount of gas liberated on the way. All stages do not need to be entered and a last flash to standard conditions is always included. The Used checkbox within the separator data area switches the correction on and off. The Setup button allows the stage characteristics to be changed by calling the dialog shown in figure 3.2b. Figure 3.2b Black Oil Table Export- Separator Correction

The values within this separator data area are loaded and stored separately from those within the Separator calculation. The SEP COPY button will copy the first five stages from the Separator Calculation ( Section 8.8 ) into the Separator Data area.The CLEAR button removes all values from within the Separator Data area. OK will reurn to the Export Table dialog with any changes stored. Cancel will reurn to the Export Table dialog with any changes ignored. Export When the data required has been entered and/or calculated, the variables selected can be exported by clicking the Export button. This brings up a small dialog which allows the user to select the table or tables to export (figure 3.2c). Figure 3.2c Black-Oil Table Export-Table Selection

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This dialog gives the user the ability to select one ,all, or a range of tables to export. If Range of Tables is chosen the range required should be entered in the editboxes provided. Note: the program will ignore empty tables or any which are found not to contain data of the required type. When the tables have been chosen press Export to bring up the file selection dialog as shown in figure 3.2d. The default file extension is .PTB Figure 3.2d Black Oil Table Export- File Selection

For each section of Input Data or results a check-box allows the user to switch on or off its export . A typical export file is shown below: * * Petroleum Experts - PVT Black Oil Export File * *Version 2 * * (BLANK LINES AND LINES WITH AN ASTERISK (*) IN COLUMN 1 * ARE IGNORED) * * The export of data is done always in Field units. * The target program will adjust to the internally selected units. * !!!!!!!!!!!!!!!!!! PVT FILE DETAILS !!!!!!!!!!!!!! * PVT FILE NAME : C:\PVTp_Files\Samples\EXAMPLE2.PVI * Exported :Tue Jul 01 14:19:39 2003 * !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! * NUMBER OF TABLES (MAX 10) 2 * DATA COLUMN IDENTIFIERS * - CAN BE IN ANY ORDER * - COLUMNS CAN BE MISSING * - ANY INDIVIDUAL ITEM > 3.4e35 = missing item * * * PRES - Pressure * GOR - Gas-Oil Ratio * OFVF - oil Formation Volume Factor * OVIS - oil Viscosity * ODEN - oil Density * OCOM - oil Compressibility * GFVF - gas Formation Volume Factor

PVTP User Guide

* GVIS - gas Viscosity


* WVIS - water Viscosity * WCOM - water Compressibility * ZFAC - Z Factor * GDEN - gas density * CGR - produced cgr * VCGR - vapour cgr * **************** VARIABLES EXPORTED **************** PRES OFVF OVIS GFVF GVIS ZFAC GDEN CGR VCGR **************************************************** ******************* UNITS **************** * The export of data is done always in Field units. * The target program will adjust to the internally selected units. **************************************************** ************** Export Table 1 **************** 1 21 70 4490.57 500 1.13787 0.699174 0.0252837 0.0108915 0.868079 2.17787 148.782 3.400000e+035 789.474 1.22244 0.55446 0.014923 0.0116471 0.800518 3.68811 151.793 3.400000e+035 1078.95 1.31142 0.456367 0.0101252 0.0128806 0.73866 5.47799 152.467 3.400000e+035 1368.42 1.39859 0.394272 0.00743207 0.014841 0.685703 7.58863 150.099 3.400000e+035 1657.89 1.47358 0.364101 0.00579315 0.0177385 0.646356 9.99918 143.45 3.76617 1947.37 1.52807 0.359921 0.00478481 0.0214534 0.626247 12.5262 132.861 14.3192 2236.84 1.56846 0.365676 0.00417554 0.0254297 0.627132 14.8588 121.408 25.4102 2526.32 1.60913 0.364538 0.00379799 0.0292646 0.643766 16.8588 111.318 35.5421 2815.79 1.65796 0.35173 0.00354774 0.0329799 0.669854 18.5944 102.341 45.023 3105.26 1.71807 0.329493 0.00337164 0.0367708 0.701709 20.1707 93.4821 54.6198 3394.74 1.79231 0.301015 0.0032435 0.0408836 0.737671 21.6729 83.7343 65.0602 3684.21 1.88546 0.268651 0.00315005 0.0456414 0.777245 23.1717 71.9518 77.1187 3973.68 2.0069 0.233701 0.00308507 0.0515667 0.820783 24.7439 56.3175 91.9082 4263.16 2.17827 0.196255 0.00304809 0.0597585 0.869804 26.5117 32.736 111.641 4490.57 3.400000e+035 3.400000e+035 0.00304525 0.0698282 0.915189 28.2346 0 134.605 4552.63 3.400000e+035 3.400000e+035 0.0030363 0.070459 0.925069 28.3179 0 134.605 4842.11 3.400000e+035 3.400000e+035 0.00299696 0.0734068 0.970954 28.6896 0 134.605 5131.58 3.400000e+035 3.400000e+035 0.00296114 0.076366 1.01653 29.0367 0 134.605 5421.05 3.400000e+035 3.400000e+035 0.00292832 0.0793391 1.0618 29.3621 0 134.605 5710.53 3.400000e+035 3.400000e+035 0.00289809 0.0823277 1.10681 29.6683 0 134.605 6000 3.400000e+035 3.400000e+035 0.00287013 0.085333 1.15155 29.9573 0 134.605 ************** Export Table 2 **************** 2 21 120 4762.12 500 1.12657 0.719748 0.0285219 0.0115443 0.894796 2.02053 131.338 0.102351 789.474 1.19068 0.577205 0.0172352 0.0121678 0.844809 3.32759 134.971 3.400000e+035 1078.95 1.25618 0.48944 0.0119973 0.0130866 0.799752 4.80777 135.006 1.03536 1368.42 1.32076 0.432725 0.00902924 0.0144248 0.761211 6.47108 132.485 5.17203 1657.89 1.38053 0.399021 0.00717403 0.0162841 0.731389 8.29879 127.648 11.2945 1947.37 1.43254 0.382002 0.00596006 0.018666 0.712786 10.2191 121.032 18.7737 2236.84 1.47799 0.372948 0.00515024 0.0214174 0.706809 12.1155 113.698 26.7604 2526.32 1.5219 0.362853 0.0045996 0.024329 0.712398 13.8959 106.523 34.6464 2815.79 1.56927 0.346985 0.00421313 0.0272862 0.726877 15.5395 99.6331 42.417 3105.26 1.62351 0.325005 0.00393186 0.0302933 0.747726 17.0746 92.644 50.4174 3394.74 1.68728 0.298432 0.00372095 0.0334323 0.773271 18.544 84.9954 59.0945 3684.21 1.76378 0.268955 0.00355996 0.0368422 0.802627 19.9931 76.0135 68.9484 3973.68 1.85801 0.237833 0.00343691 0.0407393 0.835526 21.4705 64.7643 80.6223 4263.16 1.97909 0.205749 0.00334538 0.0454958 0.872302 23.0392 49.6312 95.1359 4552.63 2.14687 0.17263 0.00328395 0.0518906 0.914226 24.8084 26.9905 114.544 4762.12 3.400000e+035 3.400000e+035 0.00326211 0.0586923 0.949802 26.3576 0 134.605 4842.11 3.400000e+035 3.400000e+035 0.00324696 0.0593548 0.961219 26.4806 0 134.605 5131.58 3.400000e+035 3.400000e+035 0.00319568 0.0617554 1.00242 26.9055 0 134.605 5421.05 3.400000e+035 3.400000e+035 0.00314931 0.0641632 1.04344 27.3017 0 134.605 5710.53 3.400000e+035 3.400000e+035 0.00310709 0.0665818 1.08428 27.6727 0 134.605 6000 3.400000e+035 3.400000e+035 0.00306844 0.0690137 1.12493 28.0213 0 134.605 ------------------- oooooooooo -------------------

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The ASCII file contains many comments maked with * to help the user. The IMPORT funtion ,however, requies the following information ◊ the number of tables to be read ◊ the variables exported PRES GOR etc. ◊ for each table :table number,number of entries,table temperature and saturation

pressure ◊ for each entry the variables selected separated by a space Important Note on Units The values transferred between the programs are done in field units Conversion to the user unit is done on IMPORT. Calc. Table and Calculate All When Calculate All is selected, the saturation pressure and CCE calculation will be carried out on all tables which contain a valid table temperature and on any table line with a valid pressure. Calc. Table is done on the viewed table only Clear Table and Clear All When Clear All is selected, and the clear is confirmed all table data is removed. Clear Table operates on the viewed table only. Copy CCE When Copy CCE is selected, and the copy is confirmed, all table data is removed. The table temperatures and pressures are replaced by those from within the CCE calculation user- defined input screen (section 8.4). Clear This option closes down the dialog and saves the values entered but does not evoke the export to file. 3.2.9 MBAL MultiI-PVT Export (*.PGD) PTG files are files which contain the data in a form which can be imported into the PVT/Fluid Properties/Import section of Petroleum Experts MBAL program. The MBAL program should have the tank model Variable PVT selected. The format is fairly general and could be used for other packages. An ASCII text file is produced by this procedure. The process is carried out using the Export option within View properties display or using the Export Option from the File Menu. The first stage in the export process is to calculate the Compositional gradient via a variation of the Compositional Gradient Calculation Input Dialog (see figure 3.2e). The only difference is a change of label on the button from Calc to Export. Input the depths or range of depths required and press on Export.. This brings up the Export dialog.

PVTP User Guide


Figure 3.2e MBAL MultiPVT Export

Click on Calc to fill in the table as shown in figure 3.2f.. The reference data used can be changed using the edit boxes above the main table. The program will calculate the compositional gradient for the selected depths. When this has been completed,the program uses the compositions at each depth to make up a black oil match table.for each depth. The pressures used to define the Black Oil flashes are automatically selected with respect to the saturation pressure. 5 pressures , including the saturation pressure are used. The data produced can be viewed via the MBAL Match Data dialog.. This display is called by clicking on one of the Match Data buttons in column 1. The automatically-set pressures can be modified manually in this dialog and the Black Oil properties re-calculated. The check box in column 2 indictes whether the pressures have been modified. When the data has been set click on Export to create the ASCII file.This action brings up the file selection dialog as shown in figure 3.2d. The default file extension is .PGD

Petroleum Experts


Figure 3.2f MBAL Export File Selection

Analysis allows the user to view the compositions calculated for each depth. See Analysis Dialog within the Calculations Chapter for more details. The calculation results can be viewed graphically using the Plot option. See the Plot Chapter for the options available within plots . Click on Main to exit the dialog and return to the summary display.

Figure 3.2f MultiPVt Export Calculation

Important Note on Units The values transferred between the programs are done in field units Conversion to the user unit is done on IMPORT.

PVTP User Guide


3.2.10 MBAL PVT with Depth - Black Oil Match Tables This dialog is called by clicking on any of the MatchData buttons within the MBAL export table (See figure 3.2f). A typical example is shown in figure 3.2g Figure 3.2g MultiPVt Black Oil Match Table

The table is the result of 5 flashes on a composition at a particular depth. The aim is to provide the data necessary for matching the Black Oil Model. The program automatically selects the pressures as 1 0ne third of saturation pressure 2 Two thirds of saturation pressure 3 Saturation pressure 4 Seven sixths of saturation pressure 5 Four thirds of saturation pressure The aim is to provide enough data to give the shape of the particuar Black Oil correlation above and below the Saturation Pressure. If the selected points are found to be unsuitable the values above and below can be adjusted by: a) Putting the table into Manual mode using the radio buttons provided b) Entering new values for pressure in the white boxes within the table

c) Click on the Calc. Button Exit will close the dialog and retain the values Cancel will close the dialog with any changes ignored. Plot allows the user to view the shape of th Black Oil curves .

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NOTE Any recalculation of the underlying MBAL PVT with depth table will invalidate and remove any manually entered pressures. A typical export file is shown below: * * Petroleum Experts - MBAL PVT with Depth Export File * * * (BLANK LINES AND LINES WITH AN ASTERISK (*) IN COLUMN 1 * ARE IGNORED) * - ANY INDIVIDUAL ITEM VALUE > 3.4e35 = missing item * * UNITS for each data item are assumed to be whatever is the current * setting at the time of export * *Export File Signature PetexPGD *Export File Version 1 * * !!!!!!!!!!!!!!!!!! PVT FILE DETAILS !!!!!!!!!!!!!! * PVT FILE NAME : C:\HAMID\AX.PVI * Exported :Sun Feb 08 17:02:49 1998 * !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! * DATA COLUMN IDENTIFIERS * * * DPTH - Depth * PRES - Pressure * TEMP - Temperature * PSAT - Bubble/Dew Point Pressure * GOR - Gas-Oil Ratio * OAPI - Oil Gravity * GGRV - Gas Gravity * WSAL - Water Salinity * MH2S - Mole H2S * MCO2 - Mole CO2 * MN2 - Mole 2 * OFVF - oil Formation Volume Factor * GFVF - gas Formation Volume Factor * OVIS - oil Viscosity * GVIS - gas Viscosity * ZLIQ - oil Compressibility * ZVAP - gas Compressibility * GFVF - gas Formation Volume Factor * CGR - produced cgr * **************** DEPTH TABLE VARIABLES EXPORTED **************** DPTH ,PRES ,TEMP ,PSAT ,GOR ,OAPI ,GGRV ,WSAL ,MH2S ,MC02 ,MN2 , **************************************************************** **************** MATCHDATA TABLE VARIABLES EXPORTED **************** PRES ,GOR ,OFVF ,OVIS ,GVIS ,ZLIQ ,ZVAP ,GFVF ,CGR , ******************************************************************** ********************** UNITS ***************************** PVTP User Guide


* Units Used in Depth Table Variables:- *feet ,psig ,degrees F ,psig ,scf/STB ,API , , , , , , , * Units Used in MatchData Variables:- *psig ,RB/STB ,centipoise ,centipoise , , ,ft3/scf ,bbls/MMscf , ******************************************************************** ********************** DATA ***************************** * NUMBER OF DEPTHS 7 * Reference Depth in feet 9369 * Reference Pressure in psig 3280 * Reservoir Temperature in degrees F 240 * Temperature Gradient in deg F/100 ft 1.8 *Data no 1 at Depth 8869 feet 8869 ,3220.42 ,231.003 ,2980.33 ,17528.4 ,59.6764 ,0.756737 ,0 ,1.234568e+038 ,1.234568e+038 ,0.00906007 , * Number of MatchData Lines 5 993.433 ,396.508 ,1.34781 ,0.138438 ,0.0141965 ,0.334204 ,0.898412 ,0.0174201 ,53.706 , 1986.9 ,1109.68 ,1.79818 ,0.0946761 ,0.0175569 ,0.552108 ,0.842573 ,0.00822854 ,42.6687 , 2980.33 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 ,0.0254712 ,1.234568e+038 ,0.814226 ,0.00531417 ,1.234568e+038 , 3477.05 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 ,0.0286318 ,1.234568e+038 ,0.842439 ,0.00471613 ,1.234568e+038 , 3973.76 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 ,0.0316125 ,1.234568e+038 ,0.876937 ,0.00429788 ,1.234568e+038 , *Data no 2 at Depth 9035.67 feet 9035.67 ,3237.14 ,234.002 ,3048.63 ,1.234568e+038 ,59.7848 ,0.763556 ,0 ,1.234568e+038 ,1.234568e+038 ,0.00887868 , * Number of MatchData Lines 5 1016.2 ,409.348 ,1.36064 ,0.135219 ,0.0142724 ,0.33949 ,0.896489 ,0.0170727 ,62.0198 , 2032.43 ,1155.64 ,1.83571 ,0.0916819 ,0.017834 ,0.560222 ,0.840694 ,0.00806241 ,50.1091 , 3048.63 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 ,0.0266022 ,1.234568e+038 ,0.811896 ,0.0052033 ,1.234568e+038 , 3556.74 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 ,0.0299055 ,1.234568e+038 ,0.843699 ,0.00463785 ,1.234568e+038 , 4064.83 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 ,0.0329984 ,1.234568e+038 ,0.881508 ,0.00424217 ,1.234568e+038 , *Data no 3 at Depth 9202.33 feet 9202.33 ,3254.66 ,237.001 ,3130.92 ,13072.7 ,59.9214 ,0.772361 ,0 ,1.234568e+038 ,1.234568e+038 ,0.00863199 , * Number of MatchData Lines 5 1043.63 ,426.478 ,1.37682 ,0.131639 ,0.0143599 ,0.345723 ,0.893948 ,0.0166547 ,74.6633 , 2087.29 ,1216.41 ,1.88403 ,0.0883227 ,0.0181829 ,0.569793 ,0.838169 ,0.00786225 ,61.9258 , 3130.92 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 ,0.0282337 ,1.234568e+038 ,0.808286 ,0.00506646 ,1.234568e+038 , 3652.75 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 ,0.0317214 ,1.234568e+038 ,0.845046 ,0.00454321 ,1.234568e+038 , 4174.56 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 ,0.0349646 ,1.234568e+038 ,0.887356 ,0.00417645 ,1.234568e+038 , *Data no 4 at Depth 9369 feet 9369 ,3280 ,240 ,3279.88 ,4316.35 ,60.7132 ,0.834684 ,0 ,1.234568e+038 ,1.234568e+038 ,0.0065 ,

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* Number of MatchData Lines 5 1093.28 ,483.188 ,1.42496 ,0.124293 ,0.0144985 ,0.354491 ,0.884976 ,0.0158165 ,273.857 , 2186.6 ,1358.06 ,1.99025 ,0.0827284 ,0.0188862 ,0.585908 ,0.831526 ,0.00748011 ,316.012 , 3279.88 ,4316.35 ,4.11191 ,0.0464585 ,1.234568e+038 ,0.76052 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 , 3826.53 ,4316.35 ,3.87211 ,0.0513914 ,1.234568e+038 ,0.834998 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 , 4373.17 ,4316.35 ,3.69423 ,0.0561634 ,1.234568e+038 ,0.910005 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 , *Data no 5 at Depth 9535.67 feet 9535.67 ,3306.98 ,242.999 ,3168.36 ,3380.86 ,60.8218 ,0.847811 ,0 ,1.234568e+038 ,1.234568e+038 ,0.00597958 , * Number of MatchData Lines 5 1056.11 ,455.891 ,1.41045 ,0.125053 ,0.0144333 ,0.345564 ,0.888033 ,0.0164925 ,360.764 , 2112.25 ,1249.86 ,1.9233 ,0.085132 ,0.0184277 ,0.574194 ,0.83661 ,0.00782229 ,453.442 , 3168.36 ,3380.86 ,3.40831 ,0.0518623 ,1.234568e+038 ,0.743622 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 , 3696.42 ,3380.86 ,3.23817 ,0.0571572 ,1.234568e+038 ,0.823709 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 , 4224.47 ,3380.86 ,3.10936 ,0.0623314 ,1.234568e+038 ,0.903482 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 , *Data no 6 at Depth 9702.33 feet 9702.33 ,3336.35 ,245.998 ,3100.22 ,3017.7 ,60.8607 ,0.853655 ,0 ,1.234568e+038 ,1.234568e+038 ,0.00574032 , * Number of MatchData Lines 5 1033.4 ,437.28 ,1.40159 ,0.125082 ,0.0144059 ,0.340151 ,0.890203 ,0.0169632 ,408.444 , 2066.82 ,1185.27 ,1.88612 ,0.0862731 ,0.0181776 ,0.567039 ,0.84003 ,0.00805995 ,532.838 , 3100.22 ,3017.7 ,3.1531 ,0.0543352 ,1.234568e+038 ,0.734882 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 , 3616.92 ,3017.7 ,3.00609 ,0.0597755 ,1.234568e+038 ,0.816837 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 , 4133.61 ,3017.7 ,2.89377 ,0.0651067 ,1.234568e+038 ,0.898189 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 , *Data no 7 at Depth 9869 feet 9869 ,3366.84 ,248.997 ,3045.5 ,2779.84 ,60.884 ,0.857745 ,0 ,1.234568e+038 ,1.234568e+038 ,0.00556968 , * Number of MatchData Lines 5 1015.16 ,421.808 ,1.39481 ,0.124852 ,0.0143902 ,0.335786 ,0.892026 ,0.0173724 ,445.867 , 2030.35 ,1134.7 ,1.85835 ,0.0870026 ,0.0179929 ,0.561257 ,0.84289 ,0.00826661 ,596.749 , 3045.5 ,2779.84 ,2.99245 ,0.0560421 ,1.234568e+038 ,0.728205 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 , 3553.09 ,2779.84 ,2.85924 ,0.0615715 ,1.234568e+038 ,0.811196 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 , 4060.66 ,2779.84 ,2.75683 ,0.0669972 ,1.234568e+038 ,0.893412 ,1.234568e+038 ,1.234568e+038 ,1.234568e+038 , ********************** END *****************************

PVTP User Guide


3.2.11 MBAL Variable Bubble Point(Oil) Export (*.PVB) PVB files are files which contain the data in a form which can be imported into the PVT/Fluid Properties/Import section of Petroleum Experts MBAL program. PVB files are files which contain the data in a form which can be imported into the PVT/Fluid Properties/Import section of Petroleum Experts MBAL program. The MBAL program should have the tank model Variable PVT selected. The format is fairly general and could be used for other packages. An ASCII text file is produced by this procedure. The process is carried out using the Export option within View properties display or using the Export Option from the File Menu. This display is initiated by selecting the Type 5 -MBAL Variable Bubble Pt. (Oil) option from the Export Types Dialog Screen. The objective is to provide a full black oil map for reinjecting gas into a dead oil to provide a range of fluids with differing Bubble Points. The dialog is split into 2 fluid types 3.2.12 Saturated These tables represent the oils properties at various saturation pressures. Data entry can be done for any of five temperatures. If the table pressure is below the oils uninjected bubble point a straightforward CCE calculation is done to the table temperature and pressure. The oils black oil properties are then calculated and reported. If the pressure is above the uninjected bubble point the following procedure is undertaken by the program: The oil is flahed to standard conditions to calculate a dead oil and associated gas composition The dead oil composition is mixed with a range of proportions of gas to get a curve of addition amount versus bubble point. The required amount of injected gas to achieve the input pressure is estimated. The estimated gas fraction is mixed with the dead oil and this combination is taken through a CCE to get the fluid's blackoil properties. The fraction of gas used is reported within the Analysis Dialog. 3.2.13 Undersaturated These tables represent the oils properties at pressures above the saturation pressure. For any of five temperatures.,there are five bubble points. Theses bubble points represent different mixtures of dead oil and gas. The procedure followed to achive these saturation pressure matching compositions is very similar to that outlined for the SATURATED table.Once the composition is determined this fluid is flashed at the table temperature and the range of input pressures to caculate the oils density ,viscosity and FVF. The data entry for the dialog is available in two forms i.e Automatic and User Selected. A typical Automatic display is shown in figure 3.2h. The table temperature is entered via the edit box provided. A set of radio buttons in the top right of the display allows the user to move between the five saturated tables.Table temperatures must be different. The labelled TABS allow selection between displaying the Saturated and Under saturated data. In automatic mode the user can enter an individual pressure range for each temperature. If the entries are to be repeated the Copy Pressures,Paste and Paste All buttons can be

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used to make the data entry easier. The Copy Pressures stores the pressure range entered. The Paste button will overwrite the current table entries with the stored values. The Paste All feature will overwrite all pressure ranges whether saturated or undersaturated with the stored values. If any of the pressure entries contradicts the other defined variables i.e. an undersaturated PSAT the user will be informed and the values adjusted. Figure 3.2h MBAL Variable PB Input Dialog

Clicking on the User Selected radio button changes the display one similar to that in figure 3.2i.

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The user can now enter up to 50 individual pressures for each temperature. Every SATURATED table must have at least one associated UNDERSATURATED entry. Clicking on the Under saturated TAB brings up a display like that in figure 3.2j in User Selected mode: Figure 3.2i MBAL Variable PB Input Dialog

The associated Saturation Table Temperature is displayed. For this temperature up to five Bubble Points can be defined. For each Bubble Point the program will create a fluid of dead oil and injected gas. This composition will then be flashed to all the pressures defined. The required Saturation Pressure is entered using the editbox provided. The user can move between the five under saturated tables by way of the 5 radio buttons in the top right corner. The pressure entries must be equal to or above the PSAT defined for the table. As with the saturated tables all the pressure entries are independent of each other. A similar automatic mode entry is provided.

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Figure 3.2j MBAL Variable PB Input Dialog

Separator Data The display contains a section for Separator Data. This allows the user to define a separator train through which the CCE liquid will be flashed to correct the Oil FVF and GOR. The processes which are used to return an oil to standard conditions can significantly change the final oil characteristics and the amount of gas liberated on the way. All stages do not need to be entered and a last flash to standard conditions is always included. The checkbox within the separator data area switches the correction on and off. The values within this separator data area are loaded and stored separately from those within the Separator calculation. The SEP COPY button will copy the first five stages from the Separator Calculation into the Separator Data area.The CLEAR button removes all values from within the Separator Data area. Once a range of entries have been made for the Saturated and Undersaturated table have been made proceed to the Calculation and Export Dialog.

PVTP User Guide


To bring up the Calculation and Export Dialog click on the Calc control button.

Exit stores the entries made and returns to Summary Screen

Cancel will clear all entries and return the user to the Summary Screen

Clear removes a table or all table entries. Volume Shift A volume shift control panel is proved to allow the user to setup and to switch on and off this feature prior to calculation . See Volume Shift and Volume Shift Setup help for more details.

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3.3 MBAL Variable Bpt. Calculation Dialog This display is initiated by selecting the Calc option from the Export MBAL Variable Bubble Point display. A typical starting display would be: Figure 3.2k MBAL Variable PB Calculation Dialog

Clicking on the TABS allows the user to move between the Saturated and Undersaturated results tables.

Click on Calc to fill in the calculated properties for all tables.

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The display becomes: Figure 3.2l MBAL Variable PB Calculation Dialog

When the data has been set click on Export to create the ASCII file.

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Analysis allows the user to view the compositions calculated for each combination of P and T. See Analysis Dialog help for more details. Where applicable the display will show the percentage of dead oil put into the composition eg. for saturated points above the original oil bubble point the display might look like this: Figure 3.2m MBAL Variable PB Analysis Dialog

PVTP User Guide


The calculation results can be viewed graphically using the Plot option. See Plot Help . When the variable is common to both saturated and undersaturated tables the plot shows both cuves eg. oil FVF: Figure 3.2n MBAL Variable PB Plot

Click on Main to exit the dialog and return to the summary display.

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3.3.1 Eclipse Type Export (*.INC) INC files are files which contain the data in a form which can be imported into an Eclipse Blackoil Simulator. The process is initiated by selecting the 6 – Eclipse(Black Oil) Format option from the Export Types Dialog Screen. The display allows the user to calculate phase properties and export them in a variety of standard Eclipse formats. The export is to an ASCII file with a default extension of .INC . Since not all Eclipse or even PVT data is available within this file, it has beeen assumed that the file will be edited by the user and "included" in the Eclipse input file. The export is on the basis of a single stream (see Streams Help) at a single temperature. The temperature is assumed initially to be the Reservoir Temperature , but it can be changed within the Eclipse Setup dialog.Multiple temperature files can be produced by merging several individual export files. The stream is selected via the listbox at the top of the dialog. The calculations are carried out over a range of pressures for each of the three phases VIZ. Oil,Gas and Water. Each has an independent range setting. Eclipse allows for a variety of PVT data types ,indicated by selection of Keywords. The Eclipse documentationl should be used as a reference on how these types are depicted and used. Figure 3.2o Eclipse Export Utility

PVTP User Guide


This dialog has a combobox for each phase .The options include: OIL No Oil Oil with Dissolved Gas PVCO + PMAX or PVTO Undersaturated Oil with Constant Dissolved Gas PVDO (+ RSCONST) Constant Oil with Dry Gas RVCONST

GAS No Gas Wet Gas with Vapourised Oil PVTG Dry Gas PVDG Dry Gas with Constant Vapourised Oil PVDG (+ RVCONST) Constant Gas with Undersaturated Oil RSCONST

OIL No Water Water included PVTW

The keywords selected are shown at the bottom of the dialog. With the Oil with Dissolved Gas option the checboxes can be used to select between the PVCO + PMAX and PVTO options NOTE on UNITS Note that Eclipse has less unit options than PVTP. It is up to the user to output in units which match the rest of the Eclipse input file. The units dialog can be used to make any changes required To proceed to the next stage of the exporting process click on the Export button

. Clear sets all options off Exit saves the current selections and closes down the dialog Cancel closes down the dialog without saving any selection changes. 3.3.2 Eclipse Export Setup Dialog This display is initiated by selecting Export from the Eclipse Export Utility dialog. The display allows the user to setup the temperature and pressures which will be used to calculate and susequently export data to file.

The calculation will be caried out at a single temperature. This is initially set at the Reservoir Temperature but it can be changed using the Edit box shown above.

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Note The calculation done on each phase is a Constant Composition Expansion (CCE). This a flash process where all the products are retained i.e. the total amount of each component at the initial conditions is the same at all the measured values, only the phase splits (K values ) have been changed.If however a dead oil or dry gas option is chosen eg. PVDO or PVGO , the composition will be flashed to standard conditions and the excess gas or oil removed prior to performing the requied P,T flashes. Separator Data In a similar way to the CCE input this display contains a section for Separator Data. This allows the user to define a separator train through which the CCE liquid will be flashed to correct the Oil FVF and GOR. The processes which are used to return an oil to standard conditions can significantly change the final oil characteristics and the amount of gas liberated on the way. All stages do not need to be entered and a last flash to standard conditions is always included. The checkbox within the separator data area switches the correction on and off. The values within this separator data area are loaded and stored separately from those within the Separator calculation. The SEP COPY button will copy the first five stages from the Separator Calculation into the Separator Data area.The CLEAR button removes all values from within the Separator Data area. This display contains radio buttons which allow the user to swap between User Selected and Automatic modes. In Automatic the pressure entries look like this. The phase entries are independent of each other. If a phase has not been requested within the Export Utility the edit boxes for that phase are hidden.

PVTP User Guide


Figure 3.2p Eclipse Export Setup

In the User Selected version the ranged input is replaced by a grid for each phase where any mixture of pressures can be entered. Select each phase by clicking on the tab at the bottom of the grid.

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Figure 3.2q Eclipse Export Setup

Additional Inputs

Where additional information is required i.e PMAX ,RSCONST and RVCONST. the appropriate edit box will appear in this area All boxes should have an entry before proceeding to the Eclipse Export Tables dialog

To bring up the Eclipse Export Tables dialog click on the Export control button.

Exit will store all entries and return the user to the Summary Screen

PVTP User Guide



Clear removes any entered values Volume Shift A volume shift control panel is proved to allow the user to setup and to switch on and off this feature prior to calculation . See Volume Shift and Volume Shift Setup (Section 4.2.3) for more details. 3.3.3 Eclipse Export Tables This dialog allows the user to initiate calculations and view the results Figure 3.2r Eclipse Export Tables

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The Calculation Screen is loaded when the Export button is pressed on the Eclipse Export Setup Dialog. The display is in the form of a three tables , one for each phase, with input values on the left and the required calculation variables calculations listed in columns on the right. Each column has a variable name and unit as a heading. Scroll bars are provided to show more variables and results. If the values have been already calculated the display will show the last set of values calculated. To the right of each table is a calculated stock tank density for each phase. This is calculated even if the phase is absent from the setup options. When all three densities are present , they are added to the export file under the DENSITY keyword as shown below: DENSITY 52.6231 62.4562 0.0642391 / -- units (lb/ft3) The display has several control buttons along the top which have the following functions: Export

This option brings up the file selection dialog as shown below. Selecting a file name with the extension .INC and pressing OK will automatically produce the required ASCII file.

PVTP User Guide


Calculate

This option recalculates the table using the latest inputs provided Plot

This generates a full sized plot of the calculated results. Layout

This options allows the user to select which columns are displayed in the results table. See Calculation Layout Display . Cancel

This option closes down the display and passes the control back to the input screen Main

This option closes down both the calculation and the input displays and passes the control back to the main PVT screen.

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3.3.4 Eclipse Compositional Export (*.PVO) The objective is to provide an ASCII file which is compatible with an Eclipse 300 PVT input. The file is exported as a PVO type including matched composition and properties. As an option the file can also contain water properties for a range of pressures. This display is initiated by selecting the 7 -Eclipse (Compositional) Format option from the Export Types Dialog Screen. A typical dialog would be as follows: Figure 3.3 Eclipse Export Dialog

Two types of unit system are provided i.e. Field and Metric. When loaded the dialog will select the system which best matches the reservoir temperature unit. Later , however, this selection can be changed using the radio buttons provided. If water PVT is required , enter the range and number of pressures required, change the water salinity to the desired value and click on the Include Water Properties checkbox. A combo box allows the desired stream to be selected. Clicking on the Export button brings up the file selection dialog. Select a name for the PVO file and click on save. Figure 3.3 Eclipse Export File Dialog

PVTP User Guide


3.3.5 PVT Temporary Files

3.3.5.1 Temporary Data File (*.PSV) This file is created at various point within the program, particularly after regression operations, to hold intermediate results. The file is not automatically deleted when a normal PVI file is closed. If a normal PVI file becomes unreadable , it is possible to rename the PSV file as PVI and use it instead. 3.4 File Operations

3.4.1 Creating a New File While working with PVT, new input or output data files can be created at any time. To create new file, from the File menu choose the New command. This command does not actually create a new and separate file, but reinitialises the program input/output data. The next step would be to choose the compositional model etc. by selecting Options from the Options menu.. 3.4.2 Opening an Existing File

Existing data files can be opened quickly and easily at any time during the current working session. To open a file, from the File menu choose the Open option. Alternatively, press the left-hand mouse button while the pointer is over the file-open icon within the PVT toolbar. The list box within the file-open dialog gives the following options: • All PVT files (*.PV*) • Data files (*.PVI) The program displays a dialog box in which the files matching your selection criteria are listed in alphabetic order. The default data directory files are automatically displayed first. To open a file, point and click the filename to recall and press ↵ or click on OK The alternative method of opening a file is to double-click on the file name. If the file you want is not listed, it is possible that: 1) it is in a different sub directory 2) it is on a different drive 3) it is of a different file type.

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3.4.3 Saving a File

When files are opened in PVT, the program copies the selected file into the computer's memory. Any changes to the file are made to the copy in memory. In the event of a power failure or computer crash, these changes would be completely lost. To prevent this, we recommend you save your data on a regular basis and especially before quitting the program. The Save command stores all the changes made in the current active file. By default, the Save command saves a file under its original name and to the drive and directory last selected. If the file is new, you will be prompted to enter a name and select a target directory: When exiting the program the user will be prompted to close any files which have been altered during the session and not saved. 3.4.4 Copying a File The Save As command allows you to make more than one copy or version of an existing file. With this command, you can save a file under the same name but to a different drive, or under a different name on the same drive. Before saving a copy to another disk, we recommend the file is first saved on your hard disk! The program displays a dialog box listing all the current files that match your selection criteria. Your default data directory is automatically displayed first. To copy a file, enter a new name in the Filename field - up to eight characters are allowed. Select a different directory or drive if desired, then press ↵ or click on OK. 3.4.5 Closing Files The CLOSE command removes the currently-displayed file and all its data from memory. If the file has been changed the user is prompted to save the file contents before closure. The Close All command removes every file that has been loaded. The Delete Calculation Results Command leaves the file composition data in place but removes the results of any calculations that have taken place. 3.4.6 Restore Temp File A temporary file with the extension *.PSV is created at various point within the program, particularly after regression operations, to hold intermediate results. The file is automatically deleted when a normal PVI file is closed. If , however, there is a computer or software failure during further processing , this command can be used to recover lost data.

PVTP User Guide


3.5 Software Key Maintenance

3.5.1 Viewing the Software Key The Dongle command activates the REMOTE software utility program that allows you to read the software protection key. This facility lets you see what programs are currently enabled, their expiry date, user authorisation codes and key number. This utility is also used to update the software key. Software keys must be updated when new programs or modules are required or the key expiry date changed. Section 2.3 describes how to use the REMOTE utility. 3.6 Printing

3.6.1 Printer Set-up Once you have selected a printer using the Windows Control Panel and selected the appropriate set-up options, printing reports is straightforward. When you are ready to print, always verify your printer is plugged in, on-line and connected to your machine. The Printer Set-up command of the File menu, allows you to change the printer set-up options. The setup can also be changed from the Report Print Dialog Screen. As all printers have varying printing capabilities, the dialog box that appears will correspond with the printer selected. Most printers allow you to select paper size and source, page orientation and number of copies. The set-up screen example that follows is for a Canon LBP III laser printer. Figure 3.5: Printer Set-up Options

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3.6.2 Printing a Report Prior to printing a report, it is always a good idea to save your data file(s). In the unlikely event that a printer error or some other unforeseen problem occurs, this simple procedure could prevent your work being lost.

To print a report, select the Reporting/Report menu option. Select the sections you wish to report on the dialog box. The program will lead you through a series of input screens to set up the required report sections. From the main dialog box, select a destination for your report. Details of how to set up a report are given in Section Figure 3.6: Reports

PVTP User Guide


3.7 Units System This section describes the system of units. The built in flexibility of the units system enables you to select any variable and define the unit of measurement to be used. This feature makes it possible to modify the units system so that it corresponds to data reports supplied by a service company or customise the units system to suit your own personal preferences. PVTP always works internally in Field units.. To facilitate data entry and output display in any units system, PVTP accepts data in the specified Input units and converts it to Field units for calculation. The results (in Field units) are converted back to the specified Output unit set if necessary. By making selections from the different categories, you can work in the units you prefer and save the results in the units required by company policy. The changes made to the units system are file specific, each holding its own unit set. The program allows you to create your own units system. To access the units system, point to the Units menu and click the mouse, or click on the icon shown above. To access the units system, point to the Units menu and click the mouse. Alternatively , point to the units icon on the PVT toolbar and click the mouse. The following screen will appear: Figure 3.7: Units Definition

3.7.1 Unit Options The Units Menu is divided into two main sections: 3.7.2 Variables Select any item from the list of variables displayed. To select an item, move the scroll box up or down, until the required variable appears on the screen.

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3.7.3 Validation Used to set up the error checking limits for each selected input variable. 3.7.4 Unit Systems The following default Units Systems are provided: • Oilfield Units • Norwegian S.I. • Canadian S.I. • German S.I. • French S.I. • Latin S.I. Customised unit systems can be created and saved under new names. Different units can be selected for both input and output. 3.7.5 Changing the Units The Input and Output units for each variable on the list can be changed. To change or customise the default Units System: • Scroll through the measurement variables list until the unit item to modify is visible on

the screen. • Select the unit category (Input and/or Output) to modify. • Select the unit field corresponding to the measurement item and click on the arrow to

its right to display the list of unit options. • Select the preferred measurement unit. 3.7.6 Validation Limits To reduce the possibility of entering incorrect data, PVTP checks that input data falls within predetermined validation limits. For most purposes, the default validation limits are adequate. For particular applications, the user can change the validation limits if required by entering new values directly from the units definition screen. Find the required variable by scrolling through the list, then enter required changes in the low and high validation limit boxes. Enter your custom validation limits in the units currently in use. To permanently attach the new validation limits to a custom units system, click Save before leaving the validation screen by clicking OK. To save changes, click Save. You will be prompted to enter a name for the new Units System. This new system can now be recalled and applied to any file. The ability to have separate input and output unit systems allows the user to work with familiar units and to create reports in any required unit system. PVT calculates internally in Oilfield Units. If some particular units have been modified during the course of a PVT session, the changes will be written into the .PVI file when the input data are saved. Irrespective of the current units system settings, recalling a previously saved .PVI file will cause PVT to revert to the units saved in the recalled .PVI file. To permanently impose a new set of units on the recalled file, open a custom units file (or use one of the internal unit sets) and then save the .PVI file. The new units settings will be used whenever the .PVI file is loaded.

PVTP User Guide


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3.8 Command Buttons The following command buttons are used in PVT. Calculate Performs the various calculations on the input parameters for the correlations

selected. Cancel Returns you to the previous screen. Any changes or modifications will be

ignored by the system. Continue Continues to the next input screen. Any changes to the fields will be saved

and retained in memory for later calculations. A warning message will be displayed when fields requiring input data are left blank.

Help Provides on screen help for PVT. For general information, press the 'ALT'

and 'H' keys together in the Main menu, or the Index button under any help screen. Specific help screens are also available for each window.

Main Returns you to the Main Application Menu. Any changes or modifications will

be saved and retained in memory by the program. OK Returns you to the previous menu. Any changes or modifications will be

retained in memory by the program. Plot Plots any calculated results and displays them on screen. Hard copies of the

screen display can be printed by selecting the Print menu option on the Plot screen.

Reset Resets the Match parameters in order to reinstate the original text book

correlations. Save Saves a current PVT file. If this is a new data file, you will be prompted for a

file name. Extract Takes a copy of the input data and calculation/analysis results and stores the

values in a user-selected file Export Among the export options , the program creates a file with PVT compositional

data which can be imported into Petroleum Exports PROSPER program or other package.

4 Models and Model Options

This chapter describes briefly the background equations and inputs to the two models available within the PVT package VIZ. the Black Oil Model the Equation Of State Model

In addition the following topics are also covered: Acentric factors Binary Interaction Parameters Volume Shift Hydrate Modelling Wax Modelling Viscosity and Thermal Conductivity Modelling Water Eos Modelling

4.1 The Black Oil Model Traditional Black Oil Modelling techniques have been applied within PVT to

• Oil • Dry and Wet Gas • Retrograde Condensate

Matching against Laboratory Data is also available. Black Oil Modelling is a technique which works back from values of density and GOR measured at known surface conditions to predict the properties at other points and the results of process changes. The technique is fast and accurate when applicable. 4.2 The Equation of State Model Equations of State were developed to give a mathematical relationship between pressure, volume and temperature. They were originally put forward as a method of interpreting the non-ideal nature of many pure substances. With time, this role has been extended successfully to predicting the properties of simple and complex mixtures. The equations used in PVT are derived from Van der Waals Equation and in common with it represent the total pressure as a summation of an attractive and a repulsive element: P total = P repulsive - P attractive The classic Van der Waals equation describes this relationship as

2va

bvRTP −−

=


where b represents the hard-sphere volume of the molecules and a the intermolecular attraction. The two cubic Equations of State which are available within the PVT package are 1) the Peng-Robinson (PR)EoS:

)()()(

bvbbvvTa

bvRTP

−++−

−=

and, 2) the Soave-Redlich-Kwong(SRK)EoS:

)()(bvvTa

bvRTP

+−

−=

In addition there is a feature within the program which allows the user to customise the general equation to suit a specific need All cubic Equations of State can be rewritten as a function of the compressibility factor Z e.g. the Peng Robinsen equation becomes

0)()23()1( 32223 =−−−−−+−− BBABZBBAZBZ and for SRK

0)( 223 =−−−++ ABZBBAZZ where

2)()(

RTPTaA =

RTbPB =

and

RTPvZ =

In addition there is a feature within the program which allows the user to customise the general equation to suit specific needs (see Section 4.3.3) 4.2.1 The Acentric Factor The acentric factor was put forward as a means of representing the non-sphericity and polarity of many compounds. The original Equation of State PV=nRT was based on a model of hard spheres which behaved in a classical and predictable fashion. The vast majority of compounds are, unfortunately, far from ideal and far from spherical. The

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Chapter 4 - Models and Model Options 3 - 39

acentric factor provides a number which can be used in the equation of state to match predicted PVT behavior with reality. To quote the authors in Molecular Thermodynamics of Fluid-Phase Equilibria by J Prausnitz and R. D. Lichtenthaler. "Acentric Factors are arbitrary and chosen for convenience" Based on deviation of some fluids from that predicted by what the corresponding states theory suggests for simple fluids, Pitzer proposed an experimental method for determining the acentric factor. It had been obseved for simple fluids that for simple fluids that the following relationship held i.e. As the Temperature (T) approached 7/10 of the critical temperature (Tc) the measured saturation pressure(Ps) approached 1/10 of the critical pressure(Pc).

101

=c

s

PP

when )

107( =

cTT

Pitzer's proposal was to use the logarithmic deviation from this relationship as a measure of acentric factor ω

0.1)(log 7.0/10 −−≡ =cTTc

s

PP

ω

The acentric factor enters the equation of state as a component which describes the change in the intermolecular attraction component with temperature a(T) . The Peng Robinson Equation is

)()()(

bvbbvvTa

bvRTP

−++−

−=

with

),()()( ωα Rc TTaTa = where the a(T) function at the critical point is given by the empirical relationship

)(45724.0)(22

C

Cc P

TRTa =

and ),( ωα RT is a function of the reduced temperature T/Tc and the acentric factor as follows

25.0 )1(1( RT−+= βα β is an empirical quadratic or cubic of the acentric factor At values of ω less than 0.49 the equation is quadratic:

22699.054226.137464.0 ωωβ −+= The estimation changes to a cubic at other values of ω :

32 0.0166660.1644231.4850300.379642 ωωωβ +−+= In addition the repulsive factor b within PR is given by:

PVTP User Guide


)(0778.0C

C

PRT

b =

Soave Redlich Kwong varies from PR in the constants within the empirical functions i.e.

)(427.0)(22

C

Cc P

TRTa =

2176.054.1480.0 ωωβ −+=

and

)(08664.0C

C

PRT

b =

Table 4.1 shows some typical acentric factors. Note that the value increases with the size of the molecule and its polarity. Table 4.1 Common Acentric Factors

Compound Acentric Factor Nitrogen N2 0.039 Carbon Dioxide CO2 0.239 Methane C1 0.011 Ethane C2 0.099 Butane nC4 0.199 Hexane C6 0.299 Octane C8 0.398 Decane C10 0.489

Acentric factors are available from the database supplied with the PVT package. The values in table 4.1 are taken from the Petroleum Experts database. The acentric factors for all components can be viewed and adjusted within the Base Composition Information Page of the PVT package. This display is selected by clicking on the View button within the Composition Input Page.

The latter display can be called by selecting Edit Composition option from the Data menu or clicking on the icon.

It is particularly important to select the right acentric factor for pseudo components. This value can be calculated automatically or input manually within the Composition Input display. This display is selected by clicking on the Properties button within the Composition Input Page.

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PVTP User Guide


4.2.2 The Binary Interaction Coefficient The cubic equations of state were originally developed for pure substances. With time their use was extended to mixtures. This extension required some method of introducing a measure of the polar and other interactions between pairs of dissimilar molecules. The binary interaction coefficient was put forward. This variable enters the calculation as a component in the intermolecular attraction a. For mixtures :

ij

N

ij

N

ji axxa ∑∑

= =

=1 1

where and are mole fractions of components i and j, respectively and : ix jx

)1( ijji kaaa −=

ijk is the binary interaction coefficient.

The attraction functions and represent the a(T) functions for each individual component. (see acentric factor help)

ia ja

Binary Interaction Coefficients represent a flexible way of moulding the ideal Equation of State to match the non-ideal reality of many mixtures. The PVT package offers the user a variety of correlations for Binary Interaction Coefficients as well as the opportunity to enter values manually. This flexibility, however, brings with it the problem of where to start when characterising a mixture. Hint on Binary Interaction Coefficients puts forward a possible approach.

The manipulations of are carried out within the BI Coefficient Dialogue: ijk

This display is selected by clicking on the B I Coeffs... button within the Composition Input Page. The latter display can be called by selecting the Edit Composition option from the Data menu or clicking on the icon.

The Select option within the Binary Interaction Coefficients Display will bring up a dialog

box which allows the user to select between the correlations available for . ijk

Choice of BI Coefficient Authors disagree on the values of binary interaction coefficients for hydrocarbon mixtures. Some suggest that kij should be set at zero for hydrocarbon↔hydrocarbon interactions, and given a value for hydrocarbon↔non-hydrocarbon and non-hydrocarbon↔non-hydrocarbon pairs . At Petroleum Experts we suggest that this approach is suitable for systems solved using the Soave-Redlich-Kwong(SRK) Equation Of State. Wih the Peng-Robinson(PR) Equation Of State the following general approach was found succesful in most cases For Volatile Oils or Condensates , try

◊ A. N. Other Correlation for Boiling Point

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◊ Bergman(PNA) and Cavett/Edmister for Acentric Factor ◊ No Binary Interaction Coefficients or a small value eg 0.05 between the C1

and heaviest component. For Heavy Oils , try

◊ Petroleum Experts Correlation for Boiling Point ◊ TWU/Edmister for Acentric Factor ◊ Binary Interaction Coefficients for all components

The PVT package offers the user a variety of correlations for binary interaction coefficients as well as the opportunity to enter values manually. The manipulations of kij are carried out within the display illustrated below:

PVTP User Guide


This display is selected by clicking on the B I Coeffs... button within the Composition Input Page. The latter display can be called by selecting the Edit Composition option from the Data menu or clicking on the icon. The Select option within the Binary Interaction Coefficients Display will bring up a dialog box which allows the user to select between the correlations available for kij. 4.2.3 Volume Shift Volume Shift arises from an inherent weakness in the 2 parameter(a and b) Equations of State in estimating liquid densities. The Peng Robinson variant is P=RT/(V-b)-a(T)/[V(V+b) +b(V-b)] In the 3 parameter version V is replaced by a corrected version Vs where Vs = V +cV c is the third parameter and is the sum of the individual xi.ci Since this correction is done after the flash equilibrium calculations, the component K values,saturation pressure and phase envelope are not affected. What is changed is the compressibility Z and anything derived from it i.e. Density,GOR,FVF,Relative Volume etc. The use of Volume Shift seems to be very attractive,since it corrects a known problem. However , there are very significant problems in using this method eg.: 1) The Equation of State is non predictive . Matching must be used to model real fluid behaviour. Volume Shift can be used to make up for bad data or inadequacies in the matching methods. This can be very dangerous particularly as there is no real control or limit to the value of c . In our experience nearly all fluids can be matched without volume shift using the methods outlined in EOS : Step by Step Guide . For this reason this method is not recommended until all other approaches have been exhausted. 2) The Volume Shift approach is a fairly crude correction factor which solves the difficulty of matching density.It does ,however, introduce other problems by breaking up the continuity of the original equation. It is not a temperature dependent function. Matching a c at one elevated temperature may cause difficulties with matching and the material balance at another. lower temperature Volume Shift is available when any equation of state model is selected within the OPTIONS display. Thereafter all relevant calculation displays and the Preferences/Calculation Tolerances contain a volume shift control panel. The control panel consists of a check box to switch on and off the correction and a button to set up the Volume Shift parameters (see Volume Shift Setup below) There are two ways of setting up volume shift within the program. The first is based on calculating ci (called Vol Shift C within the program) as a function of Zrackett Pc and Tc.. The second is based on a method from Jhaveri and Joungren (SPE 13118,1988)

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In this method Ci = bi . Si where the Vol Shift S factor Si is taken from a database or calculated from the molecular weight of the component by Si = (1-(d / MWti**e)) The selected volume shift parameter Ci or Si can be regressed upon if required (see Regression Parameter Selection) 4.2.3.1 Volume Shift Setup This dialog is loaded by the Setup button within the volume shift control panel (see example below)

All relevant calculation displays and the Preferences/Calculation Tolerances contain a volume shift control panel. A typical display is The main body of this dialog is a grid which displays the parameters used to calculate volume shift Vol Shift C and Vol Shift S and those used to calculate c and s values. All data within the grid can be edited manually and stored. The grid has a tab control to swap between streams. As described in the Volume Shift Help. 2 methods of obtaining a shift are available within the package. Radio buttons on the top right of the display allow the user to swap between the methods. Each method has a clear and calculate button to create new values. The Jhaveri and Joungren has an additional two edit boxes for the D and e variables which are used to calculate the component S values.

This button allows the user to get a feel for the degree to which the volume shift is varying the fluid properties. When presssed the program will flash the fluid to standard condition with and without the shift on. The results are presented as shown below This dialog is loaded by the Setup button within the volume shift control panel (see example below)

All relevant calculation displays and the Preferences/Calculation Tolerances contain a volume shift control panel.

PVTP User Guide


The main body of this dialog is a grid which displays the parameters used to calculate volume shift Vol Shift C and Vol Shift S and those used to calculate c and s values. All data within the grid can be edited manually and stored. The grid has a tab control to swap between streams. As described in the Volume Shift Help. 2 methods of obtaining a shift are available within the package. Radio buttons on the top right of the display allow the user to swap between the methods. Each method has a clear and calculate button to create new values. The Jhaveri and Joungren has an additional two edit boxes for the D and e variables which are used to calculate the component S values.

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This button allows the user to get a feel for the degree to which the volume shift is varying the fluid properties. When presssed the program will flash the fluid to standard condition with and without the shift on. The results are presented as shown below

The Volume Shift checkbox allows the user to switch on and off the global volume shift correction flag Exit and Save closes down the dialog with all changes retained Cancel closes down the dialog with all changes ignored The Volume Shift checkbox allows the user to switch on and off the global volume shift correction flag

PVTP User Guide


4.3 Wax Modelling Won (ref 1 Section 4.4.2) originally proposed a model for wax formation based on an ideal solution.The derivation of the basic equation is as follows: The problem is analysed in terms of a subcooled liquid and a thermodynamic cycle (see diagrams below). This analysis is outlined more fully in Prausnitz (ref.2 Section 4.4.2). The fugacity of the solid is equal to that of the solute in liquid and for the system at position 2 is given by:

0222 fxfsolid γ=

................eqn. 1

where is the mole % solute in the solvent or solubility, 2x 2γ is the liquid-phase activity

coefficient and is the standard state fugacity. 0

2f

if it is assumed that the solvent and solute are very similar making 12 =γ and equation 1 becomes

)_(2

)_(12

liquidsubcooled

solidpure

PP

x =

with P being the vapour pressure and now referred to as the ideal solubility 2x

Temperature

Pressure

SOLIDLIQUID

VAPOUR

TriplePoint

CriticalPoint

T

P2

P1

Pressure/Temperature Diagram for Pure Material

The problem can be more generally solved using the thermodynamic cycle shown in figure 2 below.

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ASSUMPTION 3 The volume change at the melting point is assumed to be negligible and these terms are ignored,giving:

TdChHT

Tpfda

t

∫∆+∆=∆>−

The entropy cycle can be written as:

dccbbadaSSSS>−>−>−>−

∆+∆+∆=∆

which in a similar way to enthalpy becomes

PddTvdTd

TC

SSt

t

P

P

T

T

pfda ∫∫

∆−

∆+∆=∆

>−

ASSUMPTION 4 again the volume change is assumed to be negligible giving

TdTC

SST

T

pfda

t

∫∆

+∆=∆>−

The entropy change at fusion is defined as:

t

ff T

HS

∆=∆

Substituting the results of the cycle in eqn 2 and rearranging gives the eqation which acts as the fundemental for many wax models:

)ln()1()1()ln(2

2

TT

Rc

TT

Rc

TT

RTH

ff tptpt

t

fS

L ∆+−

∆−−

∆=

ASSUMPTION 5 for most materials the melting point line is nearly parallel with the Pressure axis allowing the triple point temperature to be replaced with the melting point.

)ln()1()1()ln(2

2

TT

Rc

TT

Rc

TT

RTH

ff meltpmeltpmelt

t

fS

L ∆+−

∆−−

∆=

.................eqn 3 ASSUMPTION 6 Implicit in the use of this equation is that the thermodynamics of a pure substance in an ideal solution can be extended to a mixture where the solvent is non-ideal and the solid is neither ideal nor a pure single species Some points to note about this equation is that it is dominated by the Melting Point value.In essence this value determines when the solid may start to form. The other important term is the Heat of Melting which plays a role both in the formation temperature and the amount of solid formed. In its simplified form,this equation as used by Won overestimates both the Wax Appearance Temperature and the amount of wax formed.The various models question the assumptions built into this model extending the equation in various ways to remove these errors. How this equation is used and adapted within the various models is given in Model Details section

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4.3.1 Wax Model Details WON ORIGINAL

This model is outlined in reference 1 (Section 4.3.2). Won derived the equation 3 (Wax Modelling Section 4.3) and expressed it as follows:

])ln(1()1(exp[)(0

dPRTv

TT

TT

Rc

TT

RTH

xsK

Pmeltmeltp

meltt

fSi

Li

i

iSLi ∫

∆++−

∆+−

∆==

γγ

.......4

where and are the mole fractions of i in the liquid and solid respectively. ix isWon simplified this equation by assuming the second and third terms were equal to zero

and the ratio of activity coefficients )( S

i

Li

γγ

was equal to 1. This leaves a fairly simply equation which unfortunately exaggerates both the Wax Appearance Temperature and the amount of wax formed.

)]1(exp[meltt

f

i

iSLi T

TRTH

xsK −

∆==

Within the model the required values for Melting Points and Heats of Melting are taken fron the following correlations

iimelt M

MT 20172.02617.05.374 −+=

and mii

f TMH .1426.0=∆

where is the molecular Weight of component i iM WON WITH SOL PARAMS

This model is outlined in reference 4(Section 4.3.2) . In an effort to overcome the weaknesses in his original model above Won suggested that

the assumption that )( S

i

Li

γγ

was equal to 1 was in valid as it lead to and overestimation of the solubilities of C5 to C10 in the solid solution. Instead the author proposed an estimation of the activity coefficients based on modified regular solution theory. This gives a method of estimating the activity ratio based on solubility parameters. :

}])(){(exp[ 22SiLi

iSi

Li

RTv δδδδ

γγ

−−−=−−

where is the molar volume given by : iv

Li

i dMv

25

=

PVTP User Guide


iM is the molecular Weight of component i and is the liquid density of the component at 25 degrees C estimated by:

Ld 25

iiL MMed /06.13046272.08155.025 −−+=

The paper gives estimates of the solid and liquid solubility parameters δ up to C40 −

δ is the average solubility parameter for the respective phase Within this model the author uses the correlations outlined in his original model for estimationg melting points and heats of melting. CHUNG ORIGINAL

This model is outlined in reference 5 (Section 4.3.2) . This model is very similar to Won with Sol Params above.The difference lies in the assumption that the all the species in the solid are very similar and that the activity coefficient of the solid can therefore be set to 1. Equation 4 in Won Original above is modified by the introduction of solubility parameters to be:

)](1)ln()()1(exp[ 2

m

i

m

iLi

i

melt

f

i

iSLi V

vVv

RTv

TT

RTH

xsK −++−+−

∆==

−

δδ

with ∑= iim vxVWithin this model the author uses the correlations outlined in won original for estimationg melting points and heats of melting In addition the following correlations are suggested for molar volume and liquid solubility parameter.

)06.13046272.08155.0/(i

iii MMeMv −−+=

and

βββδ /235.10049.0781.0993.6 2 −−+=Li

where )ln( iM=β and is the molecular Weight of component i iM CHUNG MODIFIED

This model is outlined in reference 5 (Section 4.3.2) . This model is very similar to Won with Sol Params above.The difference lies in the correlations listed below:

)(9.0 55.0i

mi

f MTH =∆ )(8.3 786.0

ii Mv = and

βββδ /039.130395.0938.0743.6 2 −−+=Li

PEDERSEN WAX This model is outlined in reference 3 (Section 4.3.2) . The model is derived from the simplified version of equation 3 (Wax Modelling Section 4.3) used by Won i.e.

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)1()ln(2

2

TT

RTH

ff melt

t

fS

L

−∆−

=

Substituting fugacity coefficients for fugacities,this equation becomes:

)]1(exp[meltt

fiii T

TRTH

pxf +∆−

= φ

where is the fugacity of component i in the solid phase ifLiφ

is the liquid fugacity coefficient of component i

ix is the solid phase mole fraction of component i and p is the pressure

The basis for the model is the presumption that not all the high molecular weight material can form waxes. The fraction which is allowed to do so within the model comes from an empirical relationship :

])).((1[ Cpi

pitotal

iSi p

ppMiBAzz −−+−=

where is the fraction of allowed to become wax, Siz total

iz

iM is the C7+ molecular weight

iρ is the SG of component i

and is the SG of an equivalent paraffin given by: piρ

)ln(0675.03915.0 i

pi M+=ρ

A B and C are constants with the following values A = 0.8824 , B= 0.0005354 and C=0.1144 The component melting points and heats of melting are calculated using correlations proposed by Won(ref 1)

ii

mi M

MT 20172.02617.05.374 −+=

and mii

mi TMH .1426.0=∆

PVTP User Guide


4.3.2 Wax Model References 1) Continuous Thermodynamics for Solid-Liquid Equilibria: Wax Formation from Heavy

Hydrocarbon Mixtures by K.W. Won March 26 1985. ,Paper 27A presented at AIChE Spring National Meeting. Houston,TX.

2) J.M. Prausnitz , R.N. Lichtenthaler,E. Gomesde Azevedo :- Molecular Thermodynamics

of Fluid-Phase Equilibria 2nd Ed. ,Prentice-Hall ,New Jersey (ISBN: 0-13-599564-7) 3) Prediction of Cloud Point Temperatures and Amount of Wax Formation by K.S.

Pedersen SPE Production & Facilities Feb. 1995 ,46-49 4) Thermodynamics for Solid Solution-Liquid-Vapor Equilibria: Wax Phase Formation from

Heavy Hydrocarbon Mixtures. by K.W. Won , Fluid Phase Equilibria,30 (1986) 265-279 5) Thermodynamic Modelling for Organic Solid Precipitation by T H Chung,SPE 24851

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4.4 Hydrates 4.4.1 Background to Hydrates This manual is not intended to be a comprehensive guide to the subject of hydrates. A detailed explanation of hydrates is available in references 1-4 of the Hydrate Reference List. Gas Hydrates are solid meta-stable compounds which form at higher temperatures than that expected for pure water ice. Gas hydrates can be referred to as componds because they have a fixed composition. However, a hydrate is a particular type of compund which derives its formation not from covalent bonds but from weak van der Waals attraction forces. Within a hydrate, water molecules form a cage with spaces(cavities). If a gas molecule is of the right size it can occupy a cavity and weakly bond to the surrounding water molecules. This bonding makes the overall energy of the hydrate lower than that for the molecules in non-hydrate form and acts as the thermodynamic driving force for hydrate formation. The compounds formed by this type of loose entrapment are termed Clathrates. Water has been identified as forming three types of hydrates VIZ. I ,II and H (ref.1,2) For the purposes of this program we will cinsider only the more common I and II forms. The differences between the two structures derive from the number of molecules which make up a single unit. Both types of hydrate contain a variety of small and large cavities. The number and size distribution of the cavities within a hydrate determines the types and amount of gas molecules which can be held. Not all cavities need to be filled to form a stable hydrate.

PVTP User Guide


Typical of the data supplied for the two hydrate types:

Property Hydrate I Hydrate II Number of water molecules per unit cell 46 136 No. of small cavities 2 16 No of large cavities 6 8 Small diameter Angstrom 7.95 7.82 Small diameter Angstrom 8.6 9.46 Potential guest molecules-small cavity C1

CO2 N2

H2S

C1 C2

CO2 N2

H2S Potential guest molecules-large cavity C1

CO2 N2

H2S

C1 C2 C3 C4 iC4 CO2 N2

H2S With a small number of potential guests and two possible structures, the calculation of hydrate formation can be dealt with by the application of statistical mechanics (van der Waals and Platteeuw ref. 5) Estimating hydrate formation is explained in more detail in Hydrate Modelling. Inhibitors Since hydrate formation is can be an expensive process problem ,much work has been carried out to engineer its reduction or prevention. The most common methods involve any or all of the following: a) Keeping the temperature higher than the hydrate formation temperature. b) Adding bulk inhibitors such as methanol or sodium chloride which will shift the hydration curve downwards to lower temperatures and c) Adding "kinetic" inhibitors which act to slow down the formation of hydrate crystals The modelling of inhibitors is dealt with in Hydrate Inhibition. The user is encouraged to read references 1 or 2 (Section 4.4.2) to get a more in-depth view of this subject.

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4.4.2 Hydrate Modelling The thermodynamic modelling of gas hydrates is normally considered to consist of 2 steps. pure water (state 1) -> empty hydrate lattice(state 2) -> filled hydrate lattice(state H) State 2 is really hypothetical , only being used to make the calculation practical. Written in terms of chemical potentials the transition becomes.

)()( 1221 µµµµµµ −+−=− HH

The 1µµ −H term represents the gain from adsorption of the gas molecules. It is this difference that is a measure of the weak van der Waals forces which are giving the energy advantage to forming the structure. The estimation of this term is treated as a statistical gas adsorption problem and the varying aproaches to its solution make up the majority of the differences between the model options (see Hydrate Formation Pressure and Minimum Inhibitor Concentration). The difference between the chemical potential of pure water and the filled hydrate is given by

)1ln(1 ∑ ∑−−=−i j

jiciH ynRTµµ

where is the number of cavities of type i cin

and is the probability that cavity of type i is occupied by gas molecule of type j (see table in Background to Hydrates).

jiy

The important term is calculated from Langmuir adsorption theory and is given by: jiy

∑+=

kkki

jjiji fC

fCy

)1(

where and are the fugacities forgas molecule j and k calculted by the Equation of State Model.

jf kf

jiC is a temperature-dependent Langmuir adsorption constant whose value is calculated differently for the options given within the hydrate dialogs.

The term is commonly determined using the Lennard-Jones-Devonshire spherical cell model.(ref 1 Section 4.4.2).

jiC

This model requires an estimation of the potential function describing the interaction of guest molecules and the water molecules at any distance r within the cage.

PVTP User Guide


The lower the potential , the higher is the probability of finding a guest gas molecule at this position. Of the alternative methods for calculating potential the most commonly used is the Kihara (see ref 1 and 6 for more details).

In the Sloan option (ref 1) within the program the adsorption constant is derived as follows:

jiC

( ) drrkTr

kTC

R

ji2

0)exp(4

∫ −=ωπ

where R is the cavity radius and r is the distance from the cavity centre.

The experimentally fitted Kihara cell potential )(rω is calculated from :

+−+= )()(2)( 54

5

41110

11

12

δδσδδσεωRa

rRRa

rRzr

........eqn 1 and

−+−−−= −− NNN

Ra

Rr

Ra

Rr

N)1()1(1δ

where N = 4,5,10 or 11 as in eqn 1 z = the coordination number of the cavity R = the free cavity radius r = distance from the cavity centre the parameters ε , ,and a σ are experimentally derived parameters which are unique to every guest molecule.

This model outlined in the Petroleum Engineer's Handbook (ref 4 Section 4.4.2) uses a simplified fit for the adsorption constant VIZ.

)exp(TB

TAC ji =

where A and B vary for the gas molecule , the hydrate and the type of cavity.(see Background to Hydrates)

This model from reference 3 (4 Section 4.4.2) uses a function for of the type shown for the model above , but with different values for A and B.

jiC

The total chemical potential equation takes the form:

Petroleum Experts


adPRTvdT

RTh

RTPT

RTP

PwT

TwwH ln

)(00

20,01 +

∆+

∆−

∆=

−∫∫

µµµ

where )( 0,0 PTwµ∆

P is the chemical potential at the chosen reference state with temperature

and pressure 0T 0

is the specific enthalpy difference andwh∆ wv∆ is the specific volume difference going

from to T 0T

The models used vary a little in the experimentally determined values for )( 0,0 PTwµ∆ , wh∆ ,

and ∆ . Model details are available within the references quoted. wva is the activity of water within the system. The value of pure water is taken as 1. When an inhibitor is used the value of a is adjusted to include the inhibition effect. See Hydrate Inhibition for more details. 4.4.3 Hydrate Inhibition There are 2 types of hydrate inhibitor i.e. kinetic and thermodynamic. Kinetic inhibitors are designed to slow down the rate of hydrate formation by blocking or stopping crystal growth. These agents,fatty acids,amines and fatty alcohols do not stop hydrate formation, they ony shift it to a different time and place. Kinetic inhibition is outwith the scope of the PVT program at present. Thermodynamic inhibitors disrupt the order within water produced by its hydrogen bonding. This disruption reduces the activity of the water, making it less likely to form hydrates. There are two main types of thermodynamic inhibitor VIZ. alcohols (methanol,glycol) and electrolytes (NaCl,ZnCl etc.). The chemical potential water molecules in the presence of alcohols decreases because hydrogen bonds form between the water molecules and water.

H2O + CH3OH H O ….H O CH3

H

With electrolytes the water molecules form a coat of many layer around the ions in solution. This destroys the normal liquid crystal structure of water making it more difficult for the ordered hydrate structure to form. Both mechanisms result in a lowering of the water activity term a in the hydrate modelling equation.

adPRTvdT

RTh

RTPT

RTP

PwT

TwwH ln

)(00

20,01 +

∆+

∆−

∆=

−∫∫

µµµ

Activity correlations are found in references 1,2 and 7 (Section 4.4.2) for the inhibitors supported

PVTP User Guide


4.4.4 Hydrate Model References 1) Clathrate Hydrates of Natural Gases by D.S.Sloan :-Marcel Dekker Inc., New York

(ISBN: 0827 99372) 2) Hydrates of Hydrocarbons by Yuri F. Makogon :- PennWell Publishing Company,

Tulsa,Oklahoma 3) Properties of Oils and Natural Gases by K.S.Pedersen,A.Fredenslund and

P.Thomassen :- Gulf Publishing Company.Houston 4) Petroleum Engineers Handbook :- Society of Petroleum Engineers ,Richardson,Texas. 5) Platteeuw. J.C. and van der Waals. J.H. : Thermodynamic Properties of Gas Hydrates

II. Phase Equilibrium in the System, Rec. Trav. Chem.(1959),78,126-133 6) J.M. Prausnitz , R.N. Lichtenthaler,E. Gomesde Azevedo :- Molecular Thermodynamics

of Fluid-Phase Equilibria 2nd Ed. ,Prentice-Hall ,New Jersey (ISBN: 0-13-599564-7)

Petroleum Experts


4.5 Compositional Gradient 4.5.1 Background to Compositional Gradient The compositional gradient function calculates the effect of gravity on the distribution of components within the reservoir. Under the influence of gravity light components will tend to move towards the top of the structure with the heaviest having a greater abundance towards the bottom. Fig 1

fi(T,P,ni) f1i(T1,P1,ni)

With no gravity effect the fugacity of a component is a function of the temperature, pressure and composition. Fig 2

fi(T,P,ni)

f1i(T1,P1,ni,dz)

} dz

With the gravity effect introduced the fugacity also becomes a function of the change in height dz. The change in the component fugacities over the height change is given by the following equation (full derivation in ref 1.):

gdzRTMwfif

ii )/(exp[

1−=

..................... Eqn 1

The fugacity of a component at reference changes to . The size of the change

depends on the temperature T, dz, and importantly the component molecular weight .

f i 1f i

Mwi

When the component molecular weights are very different e.g. methane (18) and asphaltene (2000-20000), the gradient is at its most extreme with the composition and consequently the saturation pressure varying relatively quickly with depth.

PVTP User Guide


Fig 3

dz

P ,T ,nref ref ref

P ,T ,n1 1 1

The procedure the program follows to solve the gradient is as follows: 1 The vertical heights selected are resolved as a set of stages (see fig. 3). 2 The starting point is the matched PVT sample, which has a composition (nref), a reference pressure (Pref) and a reference temperature (Tref) associated with it. 3 From P,T and n the equation of state can calculate zfactor and density of the fluid and

the component fugacities at this point. f i4 From the fluid density and the change in height the program can estimate P1. The implication being that the composition is constant over dz. 5 T1 is calculated from the user-entered temperature gradient.

6 From P1 estimate, T1 and nref, the component fugacities can be calculated as in figure 1 i.e. no composition change due to gravity.

1f i

7 Equation 1 is the used to adjust the value and take account of the size segregation. 1f i

8 The adjusted fugacity ratio is directly related to the composition, so a new estimate of composition at 1(n1) can be calculated. 9 The pressure adjustment required at 1 is directly related to the change in composition so a new P1 can be estimated. 10 With the new P1 and n1 , steps 6-9 are repeated until the values converge i.e. the fugacity change calculated for P,T and n changing equals that predicted by equation 1. 11 The reference conditions now become P1, T1 and n2 and the second stage is calculated. 12 When all upward stages have been calculated, the program returns to Tref and Pref and does the downward stages in exactly the same way The result of this calculation is a series of pressures temperatures and compositions and depths for each of the selected depths. If you are starting from an oil and travel up the structure, the fluid will get lighter and lighter, containing more and more methane. At the some stage the composition calculated will be a gas. This is the GOC. With the Ps, Ts and compositions the equation of state can be used to calculate the properties of the fluid at each depth including saturation pressure density GOR etc. The results are normally projected graphically with the change in reservoir pressure and saturation pressure shown versus depth.

Petroleum Experts


Fig. 5

From this diagram it can be seen that the fluids are very different. They do however share a common point that is equal to the temperature and pressure at the GOC. 4.5.2 Compositional Gradient References

1) Thermodynamics of Hydrocarbon Reservoirs by A. Firoozabadi :-McGraw-Hill (ISBN: 0-07-022071-9)

2) Prediction of compositional grading in a reservoir fluid column - Montel F. and

Gouel P.L. SPE 14410

3) Compositional variations within a hydrocarbon column due to gravity - Schulte A. 55th Techn. Conf. Soc. of Petr. Eng. AIMF,Texas,Sept. 21-24,1980 SPE 9235

4) Role of Asphaltenes in Compositional Grading of a reservoir's Fluid Column -

Hirschberg A. SPE 13171

Petroleum Experts


4.6 Viscosity and Thermal Conductivity Models Various viscosity models have been introduced into the PVTp program. Only one model is active in a file at any one time. The active model is selected via the combo box which appears on all the calculation input and regression selection displays.

The models available are listed below. To obtain details of any model click on the name.

Lohrenz, Bray Clark (section 4.6.1) - based on Jossi et al with reduced density written in terms of Vcs Pedersen et al (section 4.6.2) - corresponding states model with methane as the

reference substance Zhou et al (section 4.6.3) - corresponding states model with nC14 as the reference

substance Little and Kennedy (section 4.6.4) - correlation based on oil density molecular

weight,specific gravity and weight fraction of C7+ With unmatched fluids the Pedersen model tends to give the best results. Lohrenz Bray Clark is the most commonly used model but it gives high errors for liquids if the viscosity is not matched. When matched the LBC model gives the best match. In most cases LBC is the only practical options as export formats to other packages are written in terms of LBC inputs.. The Little and Kennedy correlation is very good at predicting the viscosity of oils above bubble point. Below saturation pressure results are mixed with some fluid values being totally unsatisfactory. The thermal conductivity model that is included within PVTp is very similar in derivation to the viscosity model from Pedersen et al (section 4.6.5) The references for all the models are given in section 4.6.6

PVTP User Guide


4.6.1 Lohrenz,Bray,ClarkViscosity Model Various viscosity models have been introduced into the PVTp program. This model(ref 5) is probably the most commonly used for hydrocarbon mixtures. Is is an adaptation of a model proposed by Jossi et al (ref 11). At the core of this model is a fourth-degree polynomial in reduced density.

45

34

2321

4/14 ]10*)[( rrrr aaaaa ρρρρξηη ++++=+− −

where a1 = 0.10230 a2 = 0.023364 a3 = 0.05833 a4 = -0.040758 a5 = 0.0093324

2x is the low-pressure gas mixture viscosity and is determined by the method proposed by Herning and Zippener (ref 12)

2/1

1

2/1*

1/* i

N

iiii

N

ii MWzMWz ∑∑

==

= ηη

the individual component viscosities are given by the following expressions

94.05* 11034 rii

i Txξ

η −= for T 5.1<ri

8/55* )67.158.4(11078.17 −= −

rii

i Txξ

ηfor T 5.1>ri

iξ is the component viscosity-reducing parameter. For a mixture this variable is determined as follows:

3/2

1

2/1

1

6/1

1

−

=

−

==

= ∑∑∑

N

icii

N

iii

N

icii PzMWzTzξ

rρ in equation 1 is the mixture density divided by the critical density of the mixture.

cr ρ

ρρ =

The variation introduced by Lohrenz et al was in the calculation of the critical density. This variable was rewritten in terms of the critical volumes of the mixture components.

1

71

77)(1−

+≠=

++

+== ∑

N

Cii

cCcciic

c VzVzV

ρ

The origins of the LBC model lies in gases rather than liquids. Its dependence on the density term causes inaccuracies with viscous fluids.

Petroleum Experts


NOTES on REGRESSION Without matching the LBC model can get the viscosity of oils very wrong. The introduction of Viscosity Automatching into the PVTp program was designed to help address this weakness. In regression the program uses the component critical volumes to match lab data.Since the Vc values are not used anywhere else within the EoS models, this matching can be done in isolation. See Viscosity Matching(Section 7.10.3) for more details on the procedure used. 4.6.2 Pedersen et al Viscosity Model In this model viscosity is calculated using a corresponding states model. This method is very similar to the corresponding states thermal conductivity model . The basic model is described in reference 1.

The corresponding states theory suggests the reduced conductivity rη is a function of reduced pressure and temperature

),( rrr TPf=η

and the reduced viscosity is given by

2/13/26/1 )()()( MWPT ccr −=

ηη

The basic premise of the corresponding states theory is that the function is the same for all the similar substances within the group.

f

Pedersen et al (refs 1,3,4) have proposed the following relationship for the viscosity of mixtures.

)),()(()/()/()/(),( 02/13/2

,6/1

, ooomixomixcomixccomixcmix TPMWMWPPTTTP ηααη −= ...........1)

where )/( ,

oco

mixmixco T

TTT

αα

= and

)/( ,

oco

mixmixco P

PPP

αα

=

The subscript o indicates the reference substance methane. The critical temperature of the mixture is given by:

)])()[(

][])()[((

33/13/1

2/133/13/1

,


))])()[((

][])()[(8(

233/13/1

2/133/13/1

,

∑∑

∑∑

+

+

=

i j cj

cj

ci

ciji

cjcii j cj

cj

ci

ciji

mixc

PT

PT

zz

TTPT

PT

zzP

The molecular weight is calculated using the expression

nnwmix MWMWMWxMW +−= − )(10304.1303.2303.2

4

In function 1) the important elements still to be found are a) The viscosity of the reference substance VIZ methane

b) The correction factor xα for the mixture and the reference substance The model for the the viscosity of the reference substance is based on the work of Hanley et al (reference 9). This has been extended by Pedersen and Fredenslund (ref 1,3) to become:

),("),(')()(),( 211 TFTFTTT o ρηρηρηηρη ∆+∆++= Each element is a polynomial in temperature and methane density. See reference 1 and 4 for details. The methane density comes in the form of a modified BWR EoS.Details of this polynomial are given in reference 10. Pedersen et al have suggested that the correction factors should take the following form:

5173.0847.1310378.71 mixrimix MWx ρα −+= and 847.1031.01 rio ρα +=

NOTES on REGRESSION In general,without matching the Pedersen model gets closer to the range of petroleum mixture viscosities. There are still inaccuracies , however, particularly with viscous oils. In an effort to reduce this error a matching facility has been added to this model. Unfortunately, the main variables within the model are the component Tcs and Pcs. Since these values are set by PSAT matching etc. it is not practical to use them again for viscosity matching. As an alternative, a shift and multiplier option has been added to match viscosity with this model i.e.. Visc = Visc*Multiplier + Shift See Viscosity Matching(Section 7.10.3) for more details on the procedure used. 4.6.3 Zhou et al Viscosity Model This viscosity model is similar to the model proposed by Pedersen et al. it is also a corresponding states model. The function is less complex than that applied by Pedersen. The other significant difference is that nC14 rather than methane is used as the reference substance.

The corresponding states theory suggests the reduced conductivity rη is a function of reduced pressure and temperature

),( rrr TPf=η and the reduced viscosity is given by

Petroleum Experts


2/13/26/1 )()()( MWPT ccr −=

ηη

The basic premise of the corresponding states theory is that the function is the same for all the similar substances within the group.

f

Zhou et al (ref 6) have proposed the following relationship for the viscosity of mixtures.

),()/()/()/(),( 532041.0756972.0,

3845374.1, oooomixcomixccomixcmix TPMWMWPPTTTP ηη −−= ...........1)

where )/( ,

co

mixco T

TTT =

and )/( ,

co

mixco P

PPP =

The subscript o indicates the reference substance nC14. The viscosity of the reference substances given by the expression:

++−

++++++=

)(exp),( 2

2342

kjPiPThgPfPePdPbPaPPToη

where P is the pressure in bars and T is the temperature in degrees C. The constants used in the formula have the following values: a = -4.868729x10-6 b = 6.162691x10-3 c = -3.461585 d = 1.545022x10-9 e = -3.443880x10-6 f = 4.187426x10-3 g = -2.527380 h = 874.0397 i = -2.985316x10-4 j = 0.3435125 k = -182.6151 NOTES on REGRESSION In general,the Zhou model does not get as good an initial value as that of Pedersen et al. There are significant inaccuracies , particularly with viscous oils. In an effort to reduce this error a matching facility has been added to this model. Unfortunately as with Pedersen, the main variables within the model are the component Tcs and Pcs. Since these values are set by PSAT matching etc. it is not practical to use them again for viscosity matching. As an alternative, a shift and multiplier option has been added to match viscosity with this model i.e.. Visc = Visc*Multiplier + Shift See Viscosity Matching(Section 7.10.3) for more details on the procedure used.

PVTP User Guide


4.6.4 Little and Kennedy Viscosity Model This viscosity model has been derived empirically from measurements of pure component and petroleum mixture viscosities(ref 7). The equation is a cubic in viscosity:

( ) ( )

411

310

4987

4

6

7

4

574

473

3

4

210

)()()()()(

11

mmmmm

ccc

BBMBMBMBT

B

MBBBT

BT

BBB

ρρρρρ

γγγ

+++++

+

+++

+

+= +++

where µ is the viscosity, T is the temperature in degrees Rankin and P is the pressure in psia.

The values of and are given by the following functions: ma mb

( )Aa em logexp= ( )Bb em logexp=

A and B in turn are given by polynomial expansions:

210

398

376

2

5

47

37210

)()()()()(

)(1

mmmm

m

cc

AMAMAMAMAT

A

TAMAMA

TAAA

ρρρρ

ργ

+++++

+

+

++

+=

++

and

( ) ( )

411

310

4987

4

6

7

4

574

473

3

4

210

)()()()()(

11

mmmmm

ccc

BBMBMBMBT

B

MBBBT

BT

BBB

ρρρρρ

γγγ

+++++

+

+++

+

+= +++

with

+7cM the molecular weight of the C7+ fraction +7cγ the specific gravity of the C7+ fraction

M the average molecular weight of the mixture mρ the density of the mixture at reservoir conditions

The value of the A and B constants are given in the table below: A Value B Value 0 21.918581 -2.6941621 1 -16815.621 3757.4919 2 0.023315983 -0.31409829x10(12) 3 -0.019218951 -33.744827 4 29938.501 31.333913 5 -2802762.9 0.24400196X10(-10) 6 -0.096858449 0.700237064X10(12) 7 0.54324554X10(-5) -0.037022195 8 0.13129082 0.070811794

Petroleum Experts


9 -0.10526154X10(-5) -0.83033554X10(-9) 10 -31.680427 21.710610 11 -31.083554 4.6.5 Thermal Conductivity Model Thermal conductivity is calculated using a corresponding states model. This method is very similar to the corresponding states viscosity models . The basic model is described in reference 1.

The corresponding states theory suggests the reduced conductivity rλ is a function of reduced pressure and temperature

),( rrr TPf=λ and the reduced conductivity is given by

2/13/26/1 )()()( MWPT ccr −−=

λλ

The basic premis of the corresponding states theory is that the function is the same for all the similar sustances within the group.

f

Pedersen et al (refs 1,3,4) have proposed the following relationship for the thermal conductivity of mixtures.

)())(),()(()/()/()/(),(

int,int,0

2/13/2,

6/1,

TPTPxMWMWPPTTTP

mixoooooix

omixcomixccomixcmix

λλλααλ

+−

= −−

………………………1)

where )/( ,

oco

mixmixco T

TTT

αα

= and

)/( ,

oco

mixmixco P

PPP

αα

=

The subscipt o indicates the reference substance methane. The critial temperature of the mixture is given by:

)])()[(

][])()[((

33/13/1

2/133/13/1

,

∑∑

∑∑

+

+

=

i j cj

cj

ci

ciji

cjcii j cj

cj

ci

ciji

mixc

PT

PT

zz

TTPT

PT

zzT

with the critical pressure being given by:

))])()[((

][])()[(8(

233/13/1

2/133/13/1

,

∑∑

∑∑

+

+

=

i j cj

cj

ci

ciji

cjcii j cj

cj

ci

ciji

mixc

PT

PT

zz

TTPT

PT

zzP

The molecular weight is calculated using an expression put forward by Mo and Gubbins (ref. 8)

3/4,

3/1,

223/13/14/12/1 ]])()/[())/()/1/1(([81

mixcmixccj

cj

ci

cicjcij

i jijimix PT

PT

PT

TTMWMWzzMW −−++= ∑∑

In function 1) the important elements still to be found are PVTP User Guide


a) The thermal conductivity of the reference substance VIZ methane

b) The correction factor xα for the mixture and the reference substance Most workers suggest that the thermal conductivity can be separated into two contributions i.e. the internal and the translational:

intλλλ += tr The internal part is given by the following functions:

MWfRCp rid /)()5.2(18653.1 1int ρηλ −=

32 029725.0030182.0053432.01)( rrrrf ρρρρ −−+=

where 1η is the gas viscosity is the gas voscosity at temperature T and 1 atm. is the Ideal Gas Heat Capacity at temperature T. R is the gas constant.

idCp

rρ is the reduced density. The model for the the thermal conductivity of the reference substance is based on the work of Hanley et al (reference 9). This has been extended by Pedersen and Fredenslund (ref 1,4) to become:

),(),(),()()(),( ,,2

,11 TTFTFTTT co ρλρλρλρλλρλ ∆+∆+∆++=

Each element is a polynomial in temperature and methane density. See reference 1 and 4 for details. The methane density comes in the form of a modified BWR EoS.Details of this polynomial are given in reference 10.

Tham and Gubbins reported xα values for the smaller molecules found in hydrocarbon mixtures(ref 11). Pedersen and Fredenslund (ref 4) extended this past C7 using the function:

086.1043.20006004.01 irii MWρα += with the value for mixtures given by:

∑∑=i j

jijimix zz 5.0)( ααα ..................2)

This expression was modified by Pedersen and Fredenslund (ref 4) to be: )1()6605.2/(1 4049.2 −+= αρα rmix

where α is equal to the mixα value in equation 2) 4.6.6 Viscosity and Thermal Conductivity References

1) Properties of Oils and Natural Gases by K.S.Pedersen,A.Fredenslund and P.Thomassen :- Gulf Publishing Company.Houston

2) Pedersen K.S. et al ,"Viscosity of Crude Oil", Chem. Eng.Sci.,39,1984,pp 1011-

1016

3) Pedersen, K.S. and Fredenslund,Aa.,"An Improved Corresponding States Model

for the Prediction of Oil and Gas Viscosities and Thermal Conductivities",Chem. Eng.Sci.,42,1987,pp 182-186

4) Christensen, P.L. and Fredenslund,Aa.,"A Corresponding States Model for the

Thermal Conductivity of Gases and Liquids",Chem. Eng.Sci.,35,1980,pp 871-875

Petroleum Experts


5) Lohrenz,J.,Bray,B.G., and Clark, C. R.," Calculating Viscosities of Reservoir Fluids from Their Compositions",J.Pet.Technol.,Oct.1964,pp 1171-1176

6) Ducoulombier,D.,Zhou H.,Boned,C.,Peyrelasse,J.,Saint-Guirons,H., and Xans P.,J.

Phys.Chem. 1986,90,pp 1692-1700

7) Little,Kennedy,Soc.Pet.Eng. J.,June 1968 ,pp 157 8) Mo,K.C. and Gubbins,K.E., "Conformal Solution Theory for Viscosity and Thermal

Conductivity of Mixtures",Mol.Phys.,31,1976,pp 825-847

9) Hanley H.J.M.,McCarty,R.D. and Haynes,N.M.,"Equation for the Viscosity and

Thermal Conductivity of Methane",Cryogenics,15,1975,pp 413-417 10) McCarty,R.D.,"A Modified Benedict-Webb-Rubin Equation of State for Methane

Using Recent Experimental Data",Cryogenics,14,1974,pp 276-280

11) Jossi,J.A.,Stiel,L.I.,and Thodos,G.,"The Viscosity of Pure Substances in the Dense

Gaseous and Liquid Phases",AIChE J.,8,1962,pp 59-63 12) Herning,F.and Zippener, L.,"Calculation of the Viscosity ofTecnical Gas Mixtures

from the Viscosity of Individual Gases"Gasu. Wasserfach,79,1936,pp 69-73

PVTP User Guide


4.7 Water Modelling The presence of water in most reservoirs and surface networks creates the requirement to model the multiphase mixtures produced. The conventional equations of state such as Peng Robinson(PR) or Soave Redlich Kwong(SRK) are not adequate for reproducing the special interaction of the aqueous phase. Workers in this area (refs 1 and 2), have concentrated their efforts in modifying the attractive fuction a(T) of water and providing binary interaction coefficients between water and the other species within the mixture. Soreide and Whitson Model This model is outlined within reference 1. The main element is the introduction of a temperature dependent binary interaction coefficient(BIC), the magnitude of which depend both on the species involved and the type of phase i.e aqueous or non-aqueous. Aqueous Phase In general the value of the BIC int this phase is given by:

)1()1()1( 22

21100 swriswriswij cTAcTAcAk ααα +++++= where j represents water, csw is the salinity of the water and Tri is the reduced temperature of component i. The constants in the equation have the following values:

32

21

130

2

1

1.0

101547.2

10438.1

107863.4

0988.115742.1

8360.01001.1

7369.11120.1

−

−

−

−

=

=

=

+−=

+=

−=

x

x

x

A

A

A

i

i

i

io

α

α

ωα

ω

ω

ω

In addition the authors proposed specific correlations for N2,CO2 and H2S N2

riswswij Tcck )08126.01(44338.0)25587.01(70235.1 75.07505.0 +++−= CO2

)7222.6exp(2566.21)17837.01(23580.0)15587.01(31092.0 979.07505.0swririswswij cTTcck −−−+++−=

H2S

riij Tk 23426.020441.0 +−= Non-aqueous Phase In the non-aqueous phase only H2S is given a temperature dependent BIC:

riij Tk 05965.019031.0 +−=

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PVTP User Guide

Some of the lighter components are given the values shown below , the rest are given a value of 0.5 C1 = 0.485 C2 = 0.492 C3 = 0.5525 nC4 = 0.5091 N2 = 0.4778 CO2 = 0.1896 In addition , the normal a(T) function is replaced for water with the equation :

)1(034.0))0103.01(1(453.01 31.12/1 −+−−+= −rswr TcTα

The fact that the BICs are temperature and phase dependent means that they cannot be manually set by the user. See Streams Menu (Section 5.5) on how streams containing water may be prepared. 4.7.1 Water Modelling References 1 )Peng-Robinson predictions for hydrocarbons,CO2,N2 and H2S with pure water and NaCl brine ,I. Soreide and C.H. Whitson, Fluid Phase Equilibria,77:217-290 2) EoS Predictionsof Compressibility and Phase Behaviour in Systems Containing Water, Hyrocarbons and CO2, A.Firoozabadi,R.Nutakki,T.W. Wong and K.Aziz.SPE 15674. 3) Multicomponent CO2/Water/Hydrocarbon Phase Behaviour Modelling:A Comprehensive Study,D.Y. Kuan,P.K. Kilpatrick,M.Sahimi,L.E. Scriven and H.T.Davis, SPE 11961 4) Predicting Phase Behaviour of Water/Reservoir-Crude Systems Using the Association Concept,A.A. Shinta and A.Firoozabadi , SPE 27872

5 Main/Stream Options This section describes the PVT main menu and the data required to be input before an analysis can be performed. Data should be entered by working through the PVT menus from left to right and top to bottom. The following menus are described in this section:

• Main menu

• Options menu

• Streams menu 5.1 PVT Main Menu All PVT functions are listed as menu options. Simply select the menu required and choose an item from the list displayed. This will activate an option or display the relevant screen. Every option you select has a result you can see. You will automatically be taken through the necessary steps to enter data and perform calculations. The intention is to move from left to right across the main applications menu. To start PVT, select the appropriate icon and press ↵ or double-click the program icon. A screen similar to the following will appear:

Figure 5.1: Main Menu

The menu options across the top of the screen are the PVT main menu options. Each is described below.


5.1.1 File The File menu is a management menu with commands that enable you to open, save or create new data files. You can use this menu to move between open files and set-up printer options. 5.1.2 Options The Options menu is the starting point of PVT and the key to the program. Use this menu to define your application and principal features of the PVT model to be used. The options you select are unique to the current file and apply until changed by the user, or another file is recalled. These options also determine the subsequent screens, menus and commands which are displayed. This menu is also used to define the input and output units of measurement. A flexible system of units is provided allowing you to customise the internal units system. 5.1.3 Data Use the Data menu to define mixture compositions and properties including pseudo-components. PVT correlations can be modified to match laboratory measured data using a non-linear regression technique. In addition , grouping of components ,setting of reference conditions, and customising the equation of state are also available. 5.1.4 Calculation The Calculation menu provides you with the relevant calculation options. Calculations include critical temperature and pressure ,phase envelopes, constant volume depletion, depletion study, constant composition expansion ,differential expansion ,separator compositions, and compositional gradient and swelling tests 5.1.5 Calc. Solids The Calc. Solds menu provides you with access to calculations involving hydrates and waxes. 5.1.6 Streams Within a PVTp file the data is packaged up as streams. Each stream being equivalent to a PVT report. This menu allows you to setup new streams , delete a stream etc. 5.1.7 Reporting The Report menu is used to generate the reports of the input data, analysis data and results. Results can be viewed on the screen, sent to the Windows clipboard or saved in a file. 5.1.8 Utilities A series of useful calculators are included within the Utilities menu. These include API conversion, material balance and enthalpy balance.

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Chapter 5 - Main Options 3 - 24

5.1.9 Preferences This menu allows the user to change the look of the front screen and change some calculation options. 5.1.10 Window This menu offers the user the standard options available from an MDI (Multi Document Interface)

The PVT package can load multiple PVT Project Files each of which occupies its own window. The windows can be selected ,cascaded,arranged and tiled via this menu. 5.2 Toolbar Two toolbars are attached to the bottom of the main menu. Each icon represents one of the most used menu options. As the mouse pointer passes over the icon a short description of the option is displayed in the Statusline which is situated at the bottom of the main PVT window. When an option is unavailable the icon is greyed-out. To select an option , place the pointer over the icon button and press the left-hand mouse button. The main icons perform the following functions:

Open an existing PVT file

Save a PVT file

Select main PVT options

PVTP User Guide


Change the PVT units for this file

Select the Components for this PVT file

Change the composition of the mixture

Calculate the Critical Pressure and Temperature

Calculate the Phase Envelope

Calculate a Range of Saturation Pressures

Calculate the results of a Constant Composition Expansion

Calculate the results of a Constant Volume Depletion

Calculate the results of a Depletion Study (wellstream analysis)

Calculate the results of a Differential Liberation

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Calculate the results of a Separation Process

Calculate a Compositional Gradient

Calculate Swelling Test

Calculate Slim-tube

View mixture properties

Group mixture

Enter Lab/Match data

Regression

Exit from the PVT package

PVTP User Guide


5.3 Summary Page When a new file is created on an existing file is opened the front sheet shown in Figure 5.1 is replaced with a summary sheet showing the main points of information available for the PVT project. Figure 5.2: Summary Sheet

Multiple project files can be loaded. Switching between files is done via Window Menu or by using the Next File button on the File Status bar. Each project file can be made up of multiple streams, each containing a unique collection of data. The active stream is selected via the list box wthin the summary toolbar. The summary screen is made up of several elements which can be toggled on or off via the Preferences menu:

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If the Summary Screen is maximised a help tree appears on the right hand side of the display. Clicking on any line will bring up the appropriate help item.

Figure 5.2a: Expanded Summary Sheet

Within the display is information on whether the main calculations have been done for this file. Double clicking any of the calculation names takes the user direcly to the calculation input display.

PVTP User Guide


5.4 Option Selection The Options menu is used to define the characteristics of the PVT project. The options selected establish the input data required and the calculation options available. The selections made apply to the current session. The data entry screens, input fields and variables are limited to those relevant to your particular application. Input options may be changed at any stage of the processing. New choices may require other information to be supplied. Therefore the user is advised to ensure that all relevant input is still valid for the new option selection. To access the Options menu, point to the menu name and click the mouse or press ALT O. The following data entry screen will appear:

Figure 5.3: System Options

The entry screen is divided in three sections - System options , User information, and User Comments. Under the System options section, define your PVT model characteristics such as Method, fluid type, Separation Stages, Equation of State, etc. These selections determine information you will be required to enter later. The User Information and User Comments section of the screen allows the user to enter data , comments and dates which help identify the project and which are printed out in the report Input Data section . 5.4.1 Option Selection To select an option, click on the arrow to the right of the required field. The list of available choices will be displayed. 5.4.2 PVT Method There are three methods currently defined:

• Black Oil

• Equation of State See Chapter 4 for more details .

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5.4.3 Fluid Type The fluid type options vary with the PVT Method

• Black Oil Options available:

◊ Oil ◊ Dry and Wet Gas ◊ Retrograde Condensate

• Equation of State

No options available 5.4.4 Separator The separator options vary with the PVT Method

• Black Oil Options available:

◊ Single Stage ◊ Two Stage

• Equation of State Options available:

◊ Multi-Stage 5.4.5 Equation of State The Equation of Sate Options are described in more detail in Chapter 4 The options available are: The choice is between a series of equations provided via the main calculation library

Peng-Robinson Soave-Redlich-Kwong

5.4.6 User Information This section is designed to help the user keep track of which project is associated with the PVT file data. None of the entries are mandatory and none of the information entered in the boxes is checked. Entries available are:

◊ Company ◊ Field ◊ Location ◊ Platform ◊ Analyst

The User Information is printed as part of any PVT report.

PVTP User Guide


5.4.7 User Comments The user comments window allows the user to enter any comments which may be required to track the history of the data or calculations within the PVT file. To enter the comments area click the left hand mouse button when the cursor is over the desired point. A new line is entered in the comments block by typing Ctrl+Enter at the desired point. Pressing the Date Stamp Button places the current date and time at the end of the comments block. The Comments are printed as part of any PVT report. The Data Input procedures for the Black Oil is described in Chapter 6. The Equation of Sate Data Input options are covered in Chapter 7. 5.5 Streams Menu The PVT project file acts as a container for multiple sets of PVT data. These may be from different attempts to solve the same the same sample match eg.using different recombination GORs. They may originate from different samples at different depths or regions within a field. They may be from totally unconnected systems . Each Stream can be interpreted as equivalent to a PVTP version 1 file. This structure is explained more in section 7.0. Multi-Stream Regression allows the user to set up multiple streams and match all lab data using a common set of component properties. The streams may represent samples from different wells or surface and reservoir. See Chapter 7 for more details. The Streams Menu allows the user to manipulate these important data structures and includes: EDIT STREAM DETAILS -change stream name and comment.

ADD STREAM - copies existing streams or imports streams from other files

DELETE STREAM - removes unwanted streams.

CREATE A STREAM TO A TARGET GOR - mixes the stock tank gas and oil to create

a stream with a predetermined GOR CREATE A STREAM TO A TARGET PSAT - mixes the stock tank gas and oil to

create a stream with a predetermined saturation pressure BLEND STREAMS - mixes streams and their properties

ALLOCATE :BLEND STREAMS TO A TARGET GOR – mixes two streams using the

blending algorithm until the mixture meets the entered GOR. The program then reports the volume and weight percents required to create the mixture.

ADD WATER TO A STREAM

Create a stream with a fixed amount of water Create a stream saturated with water

See also DATA / EDIT MOLE PERCENTS

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5.5.1 Edit Stream Details This option allows the user to change the stream name and the comment associated with the stream. Load the display from the Streams|Edit details option within the STREAM MENU Select a stream using the combo box ,change the comment or name and press EXIT when complete. See also: PVT PROJECT STRUCTURE. -where streams fit in to the overall data structure SELECT COMPONENTS - this display has an option to add an empty stream EDIT MOLE PERCENTS - streams can be copied and their compositions edited using this option. ADD STREAM - copies existing streams or imports streams from other files DELETE STREAM - removes unwanted streams. 5.5.2 Add Stream This option allows the user to create a new stream from scratch,as a copy of an existing stream or by importing. The display is loaded from the Streams|Add stream menu option(see STREAM MENU)

PVTP User Guide


to create an empty stream with no components selected click on the New Empty Stream button . This will bring up the component selection dialog. To COPY Press Copy Existing Stream.This selection brings up this dialog {bmc c:\projects\dev\pvtp\winhelp\BMP_WMF\STREAMS - ADD STREAM2.BMP} To copy: 1. rename stream if required. 2. Highlight stream to copy. 3. Click on copy stream button. To IMPORT Press Import PVI File.This selection brings up this dialog

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To Import:

1. Edit the new Stream name and comment.. 2. Pressing IMPORT displays a PVT file selection dialog.Find the required file and press OK. 3.The streams within this file will appear in the import listbox. Select the required stream and press Read Stream. Import ASCII file This initiates the same import as the the File | Import option does. Stream name and comment can also be adjusted after import using the EDIT DETAILS menu option Edit the new Stream name and comment. Select a stream from the list and press COPY. See also: PVT PROJECT STRUCTURE. -where streams fit in to the overall data structure SELECT COMPONENTS - this display has an option to add an empty stream EDIT MOLE PERCENTS - streams can be copied and their compositions edited using this option. DELETE STREAM - removes unwanted streams.

PVTP User Guide


5.5.3 Delete Stream Use this option to copy an existing stream or to import a stream from another PVT project file .The display is loaded from the Streams|Delete .Stream menu option(see STREAM MENU)

Select the required stream and press Delete Stream. You will be prompted to confirm this operation. If only one stream is available the delete option is not allowed. See also: PVT PROJECT STRUCTURE. -where streams fit in to the overall data structure SELECT COMPONENTS - this display has an option to add an empty stream EDIT MOLE PERCENTS - streams can be copied and their compositions edited using this option. ADD STREAM - copies existing streams or imports streams from other files

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5.5.4 Create a Stream to a target GOR

Use this option to create a stream with a particular GOR by combining the separator gas and stock tank oil from a matched stream . The display is loaded from the Streams|Create a Stream.... menu option (see STREAM MENU) or from the icon above.

IMPORTANT NOTE When this stream is created it is done with surface gas and oil. The process therefore mimics a recombination change. If the objective is to reflect a loss or gain of gas at reservoir conditions then the approach is not entirely appropriate. The gas evolved near saturation or that present in the gas cap may be quite different to that produced from the separators. Using the swelling test or other methodologies may produce better results. The procedure for creating the stream is as follows:

Select the stream which is to be used as the source of the gas and oil. This will be flashed to surface directly or through a separator train to provide the dead oil and gas compositions. If the target GOR is to be with respect to a separator train setup the required stages

in the edit boxes provided and click on the Use Separator Train.... check box. If no selections are made in the Separator Data area the fluid will be flashed straight to stock tank conditions i.e.. standard temperature and pressure. Enter the target GOR and click on the Create Stream button. As the program iterates the iteration number and best solution to date will be

displayed

PVTP User Guide


When a solution is found ( within the convergence test limit) the stream will be created and labelled with the GOR value. On successful completion the dialog will shut down and return to the main display

The number of iterations carried out and the accuracy of the final value can be changed using the edit boxes provided. Exit will close down the dialog and retain any entries which have been made. Cancel will close down the dialog and ignore any entries which have been made. 5.5.5 Create a Stream to a target Saturation Pressure

Use this option to create a stream with a particular PSAT by combining the separator gas and stock tank oil from a matched stream . The display is loaded from the Streams|Create a Stream.... menu option(see STREAM MENU) or from the icon above.

The procedure for creating the stream is as follows: Select the stream which is to be used as the source of the gas and oil. This will be flashed to surface directly or through a separator train to provide the dead oil and gas compositions.

Enter the Temperature at which the calculation is to be done Select the phase to be produced. With mose fluids a gass and oil can be produced

with the same PSAT .See Plot Profile below. Enter the target PSAT and click on the Create Stream button.

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As the program iterates the iteration number and best solution to date will be displayed If the saturation pressure target is above the maximum possible for the mixture a

warning will appear.See Plot Profile below When a solution is found ( within the convergence test limit) the stream will be

created and labelled with the PSAT value. On successful completion the dialog will shut down and return to the main display

The number of iterations carried out and the accuracy of the final value can be changed using the edit boxes provided. Exit will close down the dialog and retain any entries which have been made. Cancel will close down the dialog and ignore any entries which have been made.

Unlike black oil models , EoS modelling is limited by the physical and mathematical realites of mixing two fluidsi.e the separator liquid and gas. In a typical system the saturation pressure of the mixture will rise from either extreme to a maximum somewhere in middle. This feature highlights this limitation by plotting the range of possible saturation pressures that can be derived from mixing the gas and oil. The typical plot below is taken from a condensate sample.

The poinst with the additional sqares around are gas. The star on the plot marks the original mixture's saturation pressure. It can be seen from thisplot that near critical fluids ,in general, will not produce a mixture saturation pressure very much above that of the original mixture. See additional help on Plotting (Chapter 11).

PVTP User Guide


5.5.6 Blend Streams Use this option to copy an existing stream or to import a stream from another PVT project file .The display is loaded from the Streams|Blend Streams menu option(see STREAM MENU) This option allows the user to mix in a controlled fashion x% of stream A with y% of stream B. All the component properties of each stream are combined using a mixing rule to form the new stream’s values. The stream produced can be assigned to a new stream,or used to overwrite an existing stream, or sent to an archive. This is done via the radio buttons within the dialogue. Select the two streams,select the percentages of each stream and click on Blend. Press on OK to exit the dialogue and retain the changes. Press on Cancel to exit the dialogue and ignore the changes.

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5.5.7 Allocate:Blend Streams to a Target GOR Use this option to copy an existing stream or to import a stream from another PVT This option allows the user to calculate the amount of two streams that would be required to produce a mixture of the desired GOR. After calculation the stream can be created. The display is loaded from the Streams|Allocate:Blend streams.... menu option(see STREAM MENU) .

IMPORTANT NOTE The calculation will assume that all the components are perfectly mixed and come to thermodynamic equilibrium. In the real case of two fluids meeting at a manifold the contact time and phase splits present may not allow this to occur The procedure for creating the stream is as follows: Select the streams which are to be blended. If the target GOR is to be with respect to a separator train setup the required stages in the edit boxes provided and click on the Use Separator Train.... check box. If no selections are made in the Separator Data area the fluid will be flashed straight to stock tank conditions i.e.. standard temperature and pressure. Enter the target GOR and click on the Calculate button. As the program iterates the iteration number and best solution to date will be displayed When a solution is found ( within the convergence test limit) the mole percents and weight percents of each stream requied will be displayed Click on Create Stream if required. On successful completion the dialog will shut down and return to the main display The number of iterations carried out and the accuracy of the final value can be changed using the edit boxes provided. Exit will close down the dialog and retain any entries which have been made. The Plot Profile button will display graphically the full range of possible fluids.

PVTP User Guide


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5.5.8 Add Water : Create a Stream with a Fixed Amount

of Water

Use this option to create a stream with a particular mole percentage of water. This operation is normally done to a matched stream . The display is loaded from the Streams|Add Water to a Stream.... menu option or from the icon above. PVT lab experiments are normally done on samples from which all the water has been removed. The PVT report must therefore be matched with no water present. This feature allows a known water to be added and the effect of the water on the phase equilibria to be calculated. A typical display would be:

Enter the mole percent of water required in the edit box provided and click on Create Stream.

PVTP User Guide


5.5.9 Add Water : Create a Stream Saturated with Water

Use this option to create a stream which contains the maximum percentage of water before a water phase forms. This operation is normally done to a matched stream . The display is loaded from the Streams|Add Water to a Stream.... menu option or from the icon above. The calculation can also be reached from the Quick Calc dialog The calculation is available in two forms: Single Point - Create a Stream. This option calculates the value at single temperature and pressure and allows the user to create a new stream containing the calculated amount of water. Range of Values. This calculates the water concentration over a range of temperature and pressures. A typical Single Point display would be:

Enter the pressure, temperature and water salinity and click on Calculate. When a value has been calculated the program allows the user to create a stream: Enter a stream name and comment if required and click on To Stream. Selecting Range of Values changes the display to:

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Enter the range of pressures and temperatures required and click on Calculate. This brings up the caculation results table.

PVTP User Guide


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Click on Calc again.

6 Black Oil Input This section describes the PVT the Data Input options for the Black Oil . 6.1 BLACK OIL PVT - General The first stage in Black Oil PVT is to select the Model and the major variations i.e. Fluid Type and Separator setup using the OPTIONS display. Figure 6.0 shows a typical Options screen for Black Oil. Figure 6.0: PVT Input Screen

The methods available are: BLACK OIL EQUATION OF STATE

The BLACK OIL method is covered in this chapter, Equation of State is dealt with in subsequent chapters. The Black Oil Method originated as a series of empirical oil correlations . With time, the methodology was extended to cover gases and condensates. The input and correlation options change with fluid type. Use the Fluid Type listbox to match the fluid under study. Depending on the Method , options of one, two, or multiple stage separator inputs may be available. When a Black Oil is used , the PVT summary screen and its icon toolbar adjust to provide the correct information and menu options. Figure 6.0a shows a typical Summary Screen.The example chosen is a Retrograde Condensate fluid using the Black Oil Method.


Figure 6.0a: PVT Input Screen

6.2 Toolbar A toolbar of icons is attached to the bottom of the main menu. Each icon represents one of the most used menu options. As the mouse pointer passes over the icon a short description of the option is displayed in the Statusline which is situated at the bottom of the main PVT window. When an option is unavailable the icon is greyed-out. To select an option , place the pointer over the icon button and press the left-hand mouse button. The icons perform the following functions: Open an existing PVT file Close an Open PVT file Select main PVT options Change the PVT units for this file

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Chapter 6 Black Oil Input 3 - 10

6.2.1 BLACK OIL PVT - Oil Select the Data | Input Data option from the main menu to display the following PVT Input data screen: Figure 6.1: PVT Input Screen

Enter the required data in the fields provided. You can move from one box to another by pressing the TAB key. Next, select the correlation methods you want to apply and click OK. 6.2.2 Match Data Enter PVT laboratory measured data to match to as shown on the example screen below. The correlations can be adjusted using non-linear regression techniques (using the Regression button) to best fit the measured data. Figure 6.2: PVT Match Data Screen

For each match data table, enter the temperature and bubble point, then enter pressure versus gas oil ratio, oil FVF and oil viscosity. Where data is incomplete or not available, leave the field blank.

PVTP User Guide


6.2.3 Regression This option is used to perform the non-linear regression which adjusts the correlations to best fit laboratory measured PVT data. The non-linear regression matching technique can be used on up to five PVT match tables, each with a different temperature. The following PVT properties can be used as match variables:

Pb Bubble point pressure. GOR Gas oil ratio versus pressure. FVF Oil formation volume factor versus pressure. Oil viscosity Oil viscosity versus pressure.

It is not necessary to match on all properties. In cases where the PVT data is incomplete or of poor quality, good results can often be obtained by matching on the best characterised parameters only. However, because bubble point can be difficult to accurately predict from correlations, it is recommended that where possible, it is used as a match parameter. The minimum data required to perform a regression match is the bubble point and GOR.

The form of the correlations for FVF are different above and below the bubble point. If the FVF at bubble point is not available, the regression may not achieve good results. When matching the oil FVF always enter bubble point data.

Figure 6.3: PVT Regression Screen

6.2.4 Match From the Regression screen, individual correlations can be matched to selected measured PVT data by:

• Selecting the correlations • Selecting the fluid properties to match to • Clicking on Match

6.2.5 Match-all All correlations can be matched to all the fluid property data in one key stroke by selecting the Match All command button.

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6.2.6 Parameters Having performed the matching process the match parameters are displayed by clicking on Parameters. The non-linear regression technique applies a multiplier - Parameter 1, and a shift - Parameter 2 to the correlations. The standard deviation is also displayed which represents the overall quality of fit. The lower the standard deviation, the better the fit.

6.2.7 Viewing the Match Parameters The Parameters button displays the PVT correlations parameters screen. This shows the match parameters and the standard deviation for each matched correlation. Use these statistics to select the best correlation for your application. A plot should be made (refer calculation and plot sections) and a visual check of the fit quality performed before making your final selection. The match parameters can all be reset (i.e. returned to the un-matched state) by selecting the reset option. The following is an example of a correlation parameters screen: Figure 6.4: PVT Match Parameters

6.2.8 Calculations In order to make a plot or listing of fluid property data, PVT must first calculate the values over a specified range of temperatures and pressures. Using the calculated data points, plots of fluid properties versus temperature or pressure can be generated. The following is an example of the Calculate | Calculations screen. If the correlations have been matched, then the fluid properties will be calculated using the modified correlations.

PVTP User Guide


Figure 6.5: PVT Calculation Set-up

6.2.9 Calculating PVT Data To generate tables and plots of PVT data: • Select Correlations (use the best matched ones) • Enter the temperature range and number of steps • Enter the pressure range and number of steps • Select whether the matched or unmatched correlations should be used

(click on Use Match Data for Calculations checkbox) • Click OK • Click Calculate to compute PVT data for the entire range of pressures and

temperatures required by your application. The following calculation screen will be displayed:

Figure 6.6: PVT Calculation Results

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6.2.10 Plotting the Calculated Data The calculated data can be displayed on a plot. The variables which are plotted are defined under the Variables option on the plot. After performing a PVT calculation click on Plot from the PVT calculation screen. • Select Pressure for the X-axis. • Select Oil FVF for the Y-axis. Figure 6.7: PVT Results Plot

Carefully examine the PVT plots for consistency with your match data. If necessary, select a different correlation and repeat the PVT calculations until you are satisfied with the results.

PVTP User Guide


6.2.11 BLACK OIL PVT - Dry and Wet Gas The program assumes that all the liquid drop out occurs at the separator. For pressure drop calculations, an equivalent gas rate is used allowing for the Condensate and water production by ensuring a mass balance is observed. 6.2.11.1 Input Data When Dry and Wet Gas is selected as the PVT option, the following Input data screen is displayed: Figure 6.8: Dry and Wet Gas PVT

6.2.11.2 Match Data Please refer to Match data in Section 6.1.1. The following fluid properties can be matched:

• GOR

• Z factor (gas compressibility factor)

• Gas FVF

• Gas viscosity All other operations are carried out as for Oil PVT. Refer to Section 6.1.1.

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6.2.12 BLACK OIL PVT - Retrograde Condensate The PVT Retrograde Condensate (Black oil) model has been developed in house by Petroleum Experts. This model predicts liquid drop out. The reservoir gas gravity is determined using the principle of mass balance for an equivalent density of the oil. 6.2.12.1 Input Data When Retrograde Condensate (Black oil) Method is selected the following input data screen is displayed: Figure 6.9: Black Oil Condensate PVT

Enter the required data. Note if tank GOR and tank gas gravity are unknown, they can be left at 0. For such cases, the total produced GOR should be entered under separator GOR. Condensate gravity is at standard conditions.

If the separator pressure is above dewpoint, then there can be no liquids production. PVT handles conflicting input data by dropping the separator pressure to atmospheric, and increasing the separator gas gravity as required to account for the liquid production indicated by the Separator GOR. The mass balance is respected at all times.

6.2.12.2 Match Data Please refer to the Match data in section 6.1.1. The following fluid properties can be matched to:

• Dew point

• Produced CGR (condensate to gas ratio)

• Z (gas compressibility factor)

• Gas viscosity

• Gas FVF The temperature and dew point must be entered for each set of match data.

PVTP User Guide


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CAUTION: When matching oil density, there should be no input pressure higher than Dew Point, since the oil density does not exist beyond that point.

All other operations are carried out as for Oil PVT. Refer to Section 6.1.1.

7 Input Data EoS This section describes the data input required for the Equation Of State PVT model. 7.1 General Project Data Structure The PVT project file acts as a container for multiple sets of PVT data. These may be from different attempts to solve the same the same sample match eg.using different recombination GORs. They may originate from different samples at different depths or regions within a field. They may be from totally unconnected systems . each Stream can be interpreted as equivalent to a PVTP version 1 file. 7.1.1 STREAMS A stream is the main structure for holding data within a PVT file. A project must have at least one stream. Each stream is independent with the following data contained within it: a) Composition This is the identification of the components, the mole percents of each and the component properties. the composition may be grouped and/or matched. Figure 7.0 shows the structure of the PVT EoS data within a stream. The most important element of this set of data is the Working Composition. This contains the components,composition and properties which can be viewed and manipulated via the View Properties display(Section 7.5). This composition is the one which is stored with the PVT file and used as the basis for Regression and the other PVT EoS calculations. The View Properties Display allows the user to manually change any component property within the Working Composition. The first step in producing a composition is to select components from one of the package databases. This is combined with values generated for Pseudo Components to produce the Initial Composition. At this stage the Working Composition and the Initial Composition are the same. Regression on this composition is shown by a Regressed Ungrouped label at various points within the PVT package. Alternatively, the composition can be Grouped and then Regressed shown by the Regressed Grouped label. Some files may have been regressed in both forms . At each stage, the new properties generated become part of the Working Composition. b)Calculation Data Calculation inputs and results are held independently for each stream. Multiple streams can be selected for each major calculation. See CCE Calculation and Phase Envelope for examples of this facility. c) Reference Data Each Stream contains its own reference data ie Standard Temperature, Standard Pressure, Reservoir Temperature,Reference Pressure and Reference Depth. These variables are set up in the Data/Reference Data dialog and within the View Properties display d) Match Data Match or Lab Data is held separately for each stream , allowing the streams to be individually regressed upon. See Match Data for more information on the types of entry required


e) Regression Data Regression selections i.e. processes to be matched to and properties used in matching are held for each stream. See Regression Parameters for more details See also SELECT COMPONENTS - this display has an option to add an empty stream EDIT MOLE PERCENTS - streams can be copied and their compositions edited using this option. ADD STREAM - copies existing streams or imports streams from other files DELETE STREAM - removes unwanted streams. EDIT STREAM DETAILS -change stream name and comment. 7.1.2 PSEUDO STORAGE An additional smaller storage area is provided for Pseudo Properties for each stream via the Pseudo Properties Display. This allows the initial values or a later selected set to be held as the active values are worked upon.

Petroleum Experts Ltd

Chapter 7- Input Data EoS 3 - 68

7.2 Selecting Components The first stage in any Equation Of State PVT project is to select the Model Type and Equation as described in Chapter 5. The next step is to select components from one of the two databases supplied with the package VIZ. Petroleum Experts or Elf.

The display which is used for component selection is shown in figure 7.1. This screen can be called by clicking on the Select Components option within the Data menu or on the icon shown above.

Figure 7.1: Component Selection

The program automatically fills the Components list box with the component names in a short label and longer ,more descriptive, form. Components can be selected or de-selected by clicking on the component name. The number of components chosen is given on the display. Up to 40 components can be selected. If pseudo components are required, the number needed should be entered in the edit box provided. The No Components button clears the pure component selections. The No Pseudos button clears any pseudo definitions that have been entered. If a reservoir or feed composition is available ,Press the Edit Composition button when all selections have been made. This action brings up the Edit Composition display.

PVTP User Guide


Alternatively, the Recombination option allows a composition to be calculated from stock tank and separator data. Clicking on this button brings up the Recombination display. this option can also be useful as a quality check on the compositional lab data. Press Exit to leave the screen with no changes recorded. The Add Stream option creates a completely empty stream with no components selected. See Streams/Add Stream and Data/Edit Mole Percents for methods of creating streams containing copied data. 7.2.1 User Database Entries

Figure 7.1a: User Database

A more extensive user database can be setup using the database create , import and edit dialogs. This may contain the same components as the petroleum experts database with different properties, or components which are not covered by the Petex database. The user database points are held within an ASCII file with a UDB extension. The directory where these files are stored is saved within the Prosper.ini file. This directory can be set using the Set User database Directory button which calls the User Database Directory Dialog. If any *.UDB files exist their names will be displayed in the combo box provided. If the file has been created with user data, but the specific UDB file is not on the users machine the components will be listed within the user area for identification but cannot be extended or reset to the original *.UDB values. See Chapter 13 for more details.



7.2.2 Recombination This display is called by clicking on the Recombination button within the Select Data base dialogue (Section 7.0). Recombination can either be used as : 1) a method of calculating the reservoir composition from separator and stock tank

compositions and volumetric properties or, 2) a quality check on feedstock analysis i.e. by comparing the recombined

composition with the lab reported composition. 7.2.2.1 MODE

The recombination calculation comes in two modes. The default version is Simplified. The mode can be changed using the radio buttons at the top right of the display. The simplified mode reflects the basic recombination done in most PVT reports.The table inputs and controls are the same as those described in more detail below for the extended mode version. One oil and one gas composition is entered . These are normally from a separator test. Additional inputs include an oil density and either a gas density or gas gravity. The GOR entered must be referenced to Stock Tank conditions.The average molecular weight can be entered directly or ,alternatively, it can be calculated automatically from the composition entered for the oil and the molecular weight of each component. For non-pseudos the molecular weight is taken from the Petroleum Experts database. Pseudo molecular weights must be entered ,either on this dialogue or via the Pseudo Properties Display. A typical Simplified display is shown in figure 7.1b.

PVTP User Guide


Figure 7.1b: Recombination Simplified

An extended recombination is shown in figure 7.1c. The reservoir fluid composition is obtained by combining the analysis of the stock tank oil,stock tank gas and the gas from up to 5 separator stages. The table at the top of the display allows the user to enter the required compositions. The first column contains the result of any recombination which has been previously carried out. For comparison purposes, the second column gives the current reservoir composition (if one has been entered). Next follow the entry colums for stock tank oil, stock tank gas and separator gas. To enter a number ,click on the appropriate cell , type in the number,click away or hit tab. After each entry, the program will automatically calculate and display the composition total and the average moleculer weight of the column. On calculating the result of recombination, the program checks that each column total ,if used, equals 100. Only separator stages for which data exists should be filled in. The program ignores any separator stages with a zero total composition. The recombination calculation is basically a mass balance. To achieve this balance additional data is requied. The Stock tank oil density is needed along with the oil ’s average molecular weight to relate oil composition in moles to volume. An entry box is provided for oil density. The average molecular weight can be entered directly or ,alternatively, it can be calculated automatically from the composition entered for the oil and the molecular weight of each component. For non-pseudos the molecular weight is taken from the Petroleum Experts database. Pseudo molecular weights must be entered ,either on this dialogue or via the Pseudo Properties Display.



Data is also required to link the amount of gas produced with respect to the stock tank oil. This is entered in the form of GOR data for the stock tank and the utilised separator stages. NOTE: All GOR data must be entered with respect to Stock Tank Barrels (STB)

Figure 7.1c: Recombination Extended

The only other additional information required is the temperature of the stock tank and separator stages. This information is used to relate moles of gas to volumes.

When all entries have been made, press the Recombine button to initiate the calculation. The results will appear in the first column of the table.

If you wish the recombined fluid to become the reservoir composition , copy the data across by clicking on the Copy Rec to Comp button.

Leave this dialogue using the Exit and Save button if you wish any results and/or changes to be recorded.

PVTP User Guide


Cancel will close down the dialogue with the loss of any changes which may have been made.

Units will bring up the standard units dialog , allowing the user to modify units without going out to the main display.

The Quick Calc button allows the user to the small calculation menu(below).When this is called the recombined fluid composition is used to produce a temporary stream which is the used to calcuate phase envelopes, saturation pressure etc.

The program at this point will create a temporay stream using the recombined composition. Calculations , including a phase envelope, can be carried out with this composition and compared directly with the other stream results.

Leave this dialogue using the Exit and Save button if you wish any results and/or changes to be recorded. Cancel will close down the dialogue with the loss of any changes which may have been made.



7.3 Edit Composition This option is only made available when components have been selected as described in section 7.1. This dialogue acts upon the working composion of the selected Stream. The stream being acted upon can be changed via the TABS at the botton of the composition grid. See PVT Project Data Structure(Section 7.0) for a more detailed description of streams.

The display which is used for composition input is shown in figure 7.2. This screen can be called by clicking on the Edit Composition option within the Data menu or on the icon shown above. It is also automatically brought up when OK is pressed on the Select Components display (section 7.1). The display shows the Working Composition as described in Section 7.0.

Figure 7.2: Composition Input

PVTP User Guide


The display is made up of several sections: Pure Component Composition

For every pure component selected an entry box will be displayed with the short version of the component label above. The amount of each component in mole percent should be registered by clicking within the box and entering a number . Tabs can also be used to move between the boxes. The sum of mole percents entered is shown at the bottom left of the display. Clicking on the component name will cause a down arrow to appear. Clicking on this arrow will produce a sub diplay(see below) of the component properties

Pseudo Component Composition For every pseudo component selected an entry box will be displayed with the number of the above. As with pure components the amount of each pseudo in mole percent should be registered by clicking within the box and entering a number . Tabs can also be used to move between the boxes. The sum of mole percents shown at the bottom left of the display includes both pseudo and pure components. The number of pseudo components required is entered using the Select Components display (section 7.0). Note The Pseudo Name can be changed to a meaningful one by calling the Pseudo Properties Display.See Pseudo Props control button. Reservoir Reference Conditions

An entry box is provided for the three main reservoir reference variables viz. ◊ Reservoir Temperature at Depth ◊ Reservoir Reference Depth ◊ Static Pressure at Depth

These numbers are entered in the units displayed at the right hand side of the box. See Section 3.4 if another set of units is required. Please note that these variables can also be changed by using the Reference Data option within the Data menu (see Section 7.7 ) Grouping/Matching

The 2 boxes within this area indicate whether the current file is Grouped or Matched to Laboratory Data. Either condition may be destroyed by choosing the Accept or View options within this display. Both choices are designed to operate with ungrouped compositions. A composition which has been grouped and/or matched after grouping will revert to the ungrouped composition . If any function is chosen which might result in loss of data , the warning shown below is issued. To view the properties of a Grouped or Matched file the View Properties option within the Data menu should be chosen.The Archive option (see Section 7.13 ) can be used to store any composition which may be useful later.



Figure 7.2.1: Composition Warning

User Database Components If any components are derived from data bases other than the Petroleum Experts database the components will be identified by red labels . Control Buttons

The control buttons have the following functions: Exit and Save This option normally stores the values entered (in memory , not on disk) and loads the component properties from the selected database. This option will destroy any grouping or matching which may have been done (see Grouping/Matching and Figure 7.2.1). In addition if any pseudo components have been entered and their properties not set this option will automatically bring up the Pseudo Properties display (see section 7. 3). Exit - No Change This option shuts down the display and ignores any changes which have been made. Pseudo Props This option activates the Pseudo Properties Display (see section 7.3) which allows the user to enter all the properties for the pseudo components or use a correlation to calculate them. This option will destroy any grouping or matching which may have been done (see Grouping/Matching and Figure 7.2.1). To view the properties of a Grouped or Matched file the View Properties option within the Data menu should be chosen. B I Coefficients This option calls the Binary Interaction Coefficients Display (see section 7.4) which allows the user to enter all the Binary Interaction Coefficients for any or all component pairs or use a correlation to calculate them.See section 4.3.2 for more background information on Binary Interaction Coefficients. View This option brings up the full Base Composition Information display (see section 7.5) which allows the user to view and change all the component properties, binary interaction coefficients etc of the pure components. This option will destroy any grouping or matching which may have been done (see Grouping/Matching and Figure 7.2.1). To view the properties of a Grouped or Matched file the View Properties option within the Data menu should be chosen. Quick Calc. This option provides the user with access to a subset of the calculation menu (see section 8.9) as a means of checking the consistency of the entered composition information. The small display provides options to calculate:

PVTP User Guide


Exit and Save closes down the dialog keeping all changes. Cancel closes down the dialog ignoring all changes. NOTE ON GRIDS In common with all grids within the program the grids displayed can be copied from and to using standard widows editing keys (Control C,Control V copy and paste etc.).

PVTP User Guide


7.4 Pseudo Properties This option is invoked by clicking on the Properties button within the Edit Composition display. It can also activated by pressing OK on the same display if no pseudo properties have been set. The pseudo name defaults to PS-1,PS-2 etc. This may be changed to something more meaningful by clicking within the name box and editing the name. All subsequent displays will show the new name. Figure 7.3 shows a typical screen

Figure 7.3: Pseudo Properties Input

The grid displayed shows the mole percents and properties of the currently active stream.The stream being acted upon can be changed via the TABS at the bottom of the grid. See PVT Project File Structure for a more detailed description of streams. It is very important that care should be taken in setting pseudo component properties as the values can have a critical effect on the results of subsequent calculations. The PVT package keeps track of when matching has occurred with a composition.This may be when the package was grouped or ungrouped. Grouping and any susequent matching is destroyed prior to entering this display. However, a composition matched while ungrouped can be displayed and manipulated with the functions described here. Any manipulation is assumed to change the match and is preceeded by a warning. The pseudo name defaults to PS-1,PS-2 etc. This may be changed to something more meaningful by clicking within the name box and editing the name. All subsequent displays will show the new name.



As no correlation will accurately model all pseudo components, it is advisable to try several options within this display before satisfying yourself that you have a match. See Hint on Method for some direction. 7.4.1 Auto Matching of Densities

Within the PVT package two liquid densities are calculated by two different methods. The first is based on an empirical correlation from Standing and Katz. The second is calculated from the Equation of State liquid compressibilty. Experience has shown that the Standing and Katz value which is derived mainly from specific gravities is always fairly close to the measured density. This display offers a powerful way of quickly setting the EoS parameters to provide a sound basis for detailed matching/regression. The option of using zero BI coefficients provides more flexibility when a phase envelope is encountered with a rapidly rising curve at the lower T and P used for the Auto Match flash. Normally, this can be left at its default value. The option of using original pseudo props can be very valuable when a condensate is being matched. Normally this type of fluid requires splitting (see EOS : Step by Step Guide ). When splitting occurs the Standing and Katz value of the mixture changes a little.i.e. the automatch reference drifts away from its original accurate value. To prevent this the automatch process can be told to use the original unsplit value from the pseudo store to calculate the Standing Katz density by putting this option on.Care should be taken however to make sure the stored value is valid. Since Volume Shift directly affects density an opportunity is given on this display to control this feature. See Volume Shift Help for more details see: Automatic Matching Calculated Oil Densities Splitting Last Pseudo The Pseudo Components represent the largest source of unknowns within a mixture. They also tend to have a significant influence on the overall mixtures characteristics. It is logical ,therefore, to concentrate on the pseudo properties when matching and regression operations are being done. Sometimes the number of pseudos does not provide enough freedom to carry out the matching required. One option for overcoming this situation is to split the last pseudo into two or more components. The program offers a facility to do this in a controlled manner. The split funtion breaks the pseudo down into two exponential distributions. The 40 components produced are then regrouped into the original mixture with the required number of pseudos. To use the function select the number of pseudos to be produced from splitting the last (using the radio buttons provided) and hit the Split button. Note that this function will be carried out in automatic mode, values can then corrected in manual if required. Since splitting destroys the original entries of Pseudo properties the Original Nos store should be used to store the best data prior to carrying out this operation

PVTP User Guide


Original Numbers Store Since Pseudo Component data is the key to the characterisation of petroleum mixtures , it is important to keep track of the link to the initial lab data. Some operations carried out on pseudo properties eg. Splitting can destroy the original entries. The program contains a facility to Store , View and Restore the original or a designated set of entries for pseudo properties. The program will automatically store the first encountered data when this dialogue is exited using the Exit and Save button. Pressing View will display the current contents of the store Store can be used at any time to overwrite the store with the values within the Pseudo Properties Table. Restore will take the values from the store and use them to replace those within the Pseudo Properties Table. The Pseudo Components to Original Values option within the Data Reset Display acts in a similar way to the Restore option , taking values from the store and replacing those in the Working PVT composition. Data Reset Display This feature is available at various points within the PVT package. The small menu allows the user to revert back to data base or stored values. See also section 7.0 General. The options are: 1) All non-pseudo components to database values. Initially all pure component property values are taken from either the Petroleum Experts or the Elf database. These numbers can be changed manually or by matching . This option will restore any changes back to those from the database. This operation also occurs if the Select Database Components display is used 2) Ungroup Composition This option would restore the composition to the Ungrouped version. Since Grouping is removed prior to entering this display , this option is not required here. 3)Pseudo components to original values. This function is identical to the Restore of original numbers. The pseudo values stored are used to replace those in the Working Composition(see Data Structure Overview.). This Pseudo Properties Display has 2 main modes which are selected using the radio buttons on the bottom right of the screen i.e. Automatic and Manual: 7.4.2 Automatic Mode In this mode the pseudo properties are calculated using the correlation chosen from the Options section. The options display is composed of two combo boxes

The top combo box contains 2 options for calculating the pseudo component boiling point viz. Petroleum Experts A. N. Other Correlation The bottom combo box contains 9 alternative methods for calculating the acentric factor(Omega) and the critical temperature, pressure and volume of a pseudo component, viz.



TWU/Edmister Bergman(PNA) and Cavett Bergman(PNA) and Cavett/Edmister Cavett/Edmister Mathew,Roland and Katz/Edmister Robinson and Peng(PNA) Lee and Kessler/Edmister Riazi and Daubert/Edmister

Choose an option from the combo box by clicking on the down arrow and then clicking on the selection. The % aromatics within the properties grid allows the user to fix a limit on the % used within the various calculations. To fix the value enter the required number in the appropriate edit box. To remove the limit blank out the value within the edit box. After choosing the options press Calc Values When back in the pseudo properties display the options are now as follows: 1)Calculate Boiling Point Tb Enter a Molecular Weight and Specific Gravity, clear the Tb value and click on Calculate. The package will calculate Tb, Tc, Pc, Vc and Omega. or 2)Calculate Specific Gravity S.G. Enter a Molecular Weight and Boiling Point , clear the S.G value and click on Calculate. The package will calculate S.G., Tc, Pc, Vc and Omega. Clear Bpts removes all the grid boiling points causing all values and derived properties to be recalculated. 7.4.3 Manual Mode In this mode all the pseudo properties can be entered or adjusted by the user. To change a value, click or double-click inside the appropriate box , type in the number and tab or click away. NOTE ON GRIDS In common with all grids within the program the grids displayed can be copied from and to using standard widows editing keys (Control C,Control V copy and paste etc.). 7.4.4 Hint on Method For Volatile Oils or Condensates , try ◊ A. N. Other Correlation for Boiling Point ◊ Bergman(PNA) and Cavett/Edmister for Acentric Factor ◊ No Binary Interaction Coefficients or a small value eg 0.05 between the C1 and heaviest component. For Heavy Oils , try ◊ Petroleum Experts Correlation for Boiling Point ◊ TWU/Edmister for Acentric Factor ◊ Start with a small value eg 0.05 between the C1 and heaviest component.

PVTP User Guide


7.4.5 Auto-Matching of Densities and Viscosities

Within the PVT package two liquid densities are calculated by two different methods. The first is based on an empirical correlation from Standing and Katz . The second is calculated from the Equation of State liquid compressibilty. Experience has shown that the Standing and Katz value which is derived mainly from specific gravities is always fairly close to the measured density at standard conditions. The Equation of State value suffers from the main problem of the method i.e. the EoS equation will not generally predict an accurate value from initial entries. Matching to laboratory data must always be done before any calculated value can be used with confidence. A wayward set of EoS parameters normally shows up as a large deviation between the two density values when the mixture is subject to a Constant Composition Expansion at standard conditions (60 deg F , 1 atm.) This method allows the user to tune the parameters of the greatest unknowns within the mixture i.e. the pseudos to bring the densities in line. We advise that this option is used right at the start after the mixture composition has been entered,however, if an existing file is being used enter the procedure below at step 3 The complete method would then be: 1. Select a NEW PVT file and enter Equation of State Options 2. Select Components and Enter the Composition (section 7.1-7.2) 3. Select Pseudo Props option from the Edit Composition Display (section 7.2) to bring up

screen as in figure 7.3 4. Enter values for pseudo(s) Molecular Weight and Specific Gravity . 5. Select Automatic mode and press Options. This will bring up the screen as in figure 7.4 6. Select a method for Boiling Point and TC,PC,Omega calculation. Press OK 7. Press on the Auto Match button . The PVT package will now automatically go through a process of a) Adjusting the pseudo(s) boiling point(s) b) Calculating new Tc Pc etc. c) Flashing at standard condition to find the difference in densities d) Based on the difference found re-adjust and repeat or exit process



The matching will halt when a match has been found to within 1% or 20 iterations have been completed. If no match is made try adjusting the pseudo properties or selecting new options in step 6 8. With densities OK now use the binary interaction coefficient(s) to match the saturation

pressure at reference conditions. Normally only one coefficent (heaviest component -lightest component ) is required (section 7.4). This matching does not greatly affect the densities.

When this procedure is followed most petroleum mixtures will immediately give close to the measured values eg.separator GOR ,liquid dropout etc. Any differences can be readily reduced using the PVT packages regression functions(section 7.9). This procedure is normally carried out with zero-ed Binary Interaction Coefficients . Auto Match automatically stores and zeros the BI Coefficients . Ater matching the coefficients are restored.The check box on the display allows the user to skip the zeroing step , giving more flexibilty with difficult mixtures. 7.4.6 AutoMatching Viscosities Selecting AutoMatch will also automatch the viscosity of an oil. This changes the Vc values to bring the LBC calculated oil viscosity to a more reasonable level. By default, this operation will automatically be carried out if the AutoMatch button is operated. A checkbox allows the user to switch this feature off. Lohrenz , Bray and Clark (see Section 4.6.1) is the most commonly used viscosity model but it tends to give high errors for oils.The Little and Kennedy correlation (see Section 4.6.4) is very good at predicting the viscosity of oils above bubble point. Below saturation pressure results are mixed with some fluid values being totally unsatisfactory. This Automatching feature follows the procedure outlined below:

Find the type of fluid. If the fluid is not an oil do not proceed Find the saturation pressure at the reference temperature Use the Little and Kennedy model to calculate the viscosity of the oil at a pressure

just above saturation Adjust the Vc values of the pseudo components until the LBC viscosity matches

that predicted by Little and Kennedy 7.4.7 Splitting/Profilling Last Pseudo

The Pseudo Components represent the largest source of unknowns within a mixture. They also tend to have a significant influence on the overall mixtures characteristics. It is logical ,therefore, to concentrate on the pseudo properties when matching and regression operations are being done. Sometimes the number of pseudos does not provide enough freedom to carry out the matching required. One option for overcoming this situation is to split the last pseudo into two or more components.

PVTP User Guide


The program offers a facility to do this in a controlled manner. The split funtion breaks the pseudo down into a distribution defined by the Split Method(see Advanced Splitting Dialog). The 40 components produced are then regrouped into the original mixture with the required number of pseudos. To use the function hit the Split in 2 button. Alternatively, many more options are available be clicking on the Advanced button. This includes profiling a pseudo component . See also Decontamination Procedure (Appendix C) on how this feature helps with decontamination. Note that this function will be carried out in automatic mode, values can then corrected in manual if required. Since splitting destroys the original entries of Pseudo properties the Original Nos store should be used to store the best data prior to carrying out this operation ( see section 7.3.5 ).



7.4.8 Original Numbers Store

Since Pseudo Component data is the key to the characterisation of petroleum mixtures , it is important to keep track of the link to the initial lab data. Some operations carried out on pseudo properties eg. Splitting can destroy the original entries. The program contains a facility to Store , View and Restore the original or a designated set of entries for pseudo properties. The program will automatically store the first encountered data when this dialogue is exited using the Exit and Save button. Pressing View will display the current contents of the store as shown in figure 7.4a. Store can be used at any time to overwrite the store with the values within the Pseudo Properties Table. Restore will take the values from the store and use them to replace those within the Pseudo Properties Table. The Pseudo Components to Original Values option within the Data Reset Display acts in a similar way to the Restore option , taking values from the store and replacing those in the Working PVT composition (see Section 7.3.4). 7.4.9 Advanced Splitting Dialog See also Decontamination Procedure (Appendix C) The Advanced Splitting Dialog is called via the Advanced button on the Pseudo Properties display. As the name implies this display allows the user to have more control over how pseudo splitting is done, both in terms of the distribution of components and where the split limits are set. This can be very beneficial in

dealing with difficult fluids operating with multiple samples at varying depths and decontaminating samples

Normally, this operation would be carried out on a single pseudo eg. C7+ on C10+ and typical display would be:

PVTP User Guide


Figure 7.4a: Advanced Splitting Dialog

The table shows how the splitting algorithm has broken down the pseudo component giving each C number a composition . From the composition the program corrects the database MWts and SGs to match the pseudo from which the table was created. The split method determines the shape of the composition distribution. Use the combo box to change the split method and press recalculate split to activate the change. 7.4.10 Split Profiles An important option within the split methods is to Follow Profile .This feature allows the user to determine all or part of the component distribution. this can be extremely helpful in dealing with contamination or fluids with distinctive distributions eg. biodegraded fluids. To set up a profile click on the Setup Profile button. This brings up the Split Profile Creation dialog where the relevant data can be entered. select the Follow Profile method and press recalculate split. The split algorithm will give the Cn components the values defined and follow a declining distribution for the rest. Once an initial distribution is settled upon , the user can then define how the splitting is done. using initially the Split Number radio buttons. Select the number of pseudos to be created and hit the Set Even Split button. The display will change to one like this:



Figure 7.4b Advanced Splitting Dialog2

The split boundaries are confirmed by the table colours and the details which have appeared for the new 3 pseudo components. The split can be changed from this even distribution by clicking on the spin buttons beside the newly defined pseudos.

Once the split is defined the program automatically calculates a MWT and SG for each pseudo. From these values and a correlation a BPt. is set. From the BPt and a second correlation all the important EoS numbers are calculated for the pseudo. As for the Pseudo Properties display, the correlation can be selected by the user using the combo boxes provided.

The AutoMatch feature is also proved on this display to allow the user to work on the new pseudo values prior to accepting the results. Using Automatch does not effect the split it changes only some of the properties associated with the resultant pseudos.

PVTP User Guide


Similarly , the user is provided with access to the Binary Interaction Coefficients Dialog from this display.

. This button brings up the standard Quick Calc display , allowing the user to calculate the effects of the completed split.

Plotting allows the user to see the trend in compositions and properties.

This option removes all pseudos which have been created and returns the display to a single pseudo entry.

Click on this button when you are happy with all the changes that have been made. This will return the program to the Pseudo Properties display.

This option clears all changes and returns the program to the Pseudo Properties display.



7.4.11 COPYING A SPLIT

This option is useful for complex systems where samples have been taken at various depths and a compositional gradient analysis is to be done to prove linkage between the samples. If another stream within the file has been through a splitting operation and the detailed information on the split is stored. ,the file name will appear in the list box. Selecting the stream name and clicking on Copy stream Split will cause the program to match the current streams split to the one stored for the other stream. This synchronisation of pseudos helps the streams to be similarly characterised and the compositional gradients of each stream to align. 7.4.12 Split Profile Dialog See also Decontamination Procedure (Appendix C) This Dialog is called via the Setup Split Profile button on the Advanced Splitting Dialog. A typical display looks like this:

PVTP User Guide


Figure 7.4 c Split Profiling Dialog

Enter the Mole% of each component that you want the split routine to follow. Only key areas should be profiled eg. the components with maximum contamination. The program will fill in the other components using a standard distribution.

Plotting allows the user to see the trend in the compositions that have been entered.

This option removes all entries

Click on this button when you are happy with all the entries that have been made. This will

return the program to the Advanced Splitting display.



This option clears all changes and returns the program to the Advanced Splitting display. 7.4.13 COPYING A PROFILE

If another stream within the file has a profile stored its name will appear within the listbox. To copy a profile select the stream name an click on Copy.

PVTP User Guide


7.5 Binary Interaction Coefficients This option is invoked by clicking on the B I Coeffs... button within the Edit Composition display. The grid displayed shows the pseudo properties of the currently active stream.The stream being acted upon can be changed via the TABS at the bottom of the grid. See PVT Project File Structure(section 7.0) for a more detailed description of streams. The basis for using Binary Interaction Coefficients is described in section 4.3.2 . As with pseudo properties, it is very important that care should be taken in the choice of coefficients. Again no correlation will accurately model all mixtures. The BI Coefficient acts as matching variable which bends the idealised cubic Equation of state to meet the measured properties of the real world mixture. It is therefore, advisable to try several options within this display before satisfying yourself that you have a match for the project conditions(see also Hint on Method 7.3.1). Figure 7.5 shows a typical screen.

Figure 7.5: Binary Interaction Coefficients

Two combo boxes are available at the top of the display which allows the user to select a correlation. There are two choices for pure components i.e. Peng Robinson Soave Redlich Kwong In addition, there are three choices for pseudo components i.e. Petroleum Experts Method Molecular Weight Correln Semi-Theoretical Method Choose an option from the combo box by clicking on the down arrow and then clicking on the selection. Press on Calculate New Values to get the recalculated .BI Coefficients Any value of BI coefficient can be changed by clicking within the displayed table and entering a value.



Press Exit and Save to register the changes made. It is also advisable to save the file if many edits have been made. Quick Calc. This option provides the user with access to a subset of the calculation menu as a means of checking the consistency of the entered composition information. The small calculation display provides the following options: Phase Envelope Critical Point (Temperature and Pressure) Saturation Pressure (at the reference temperature) Flash at Standard Conditions Flash Through Separator Stages

NOTE ON GRIDS In common with all grids within the program the grids displayed can be copied from and to using standard widows editing keys (Control C,Control V copy and paste etc.). 7.6 Grouping and Properties Information This display can be called directly from the main Data menu by selecting the View Properties option. In addition, the screen is also invoked by clicking on the View button within the Edit Composition display or by selecting Group on the Grouping Display.(see section 7.6). Figure 7.7 shows a typical display for a grouped PVT project.

Figure 7.7: Grouping and Properties

PVTP User Guide


The stream being acted upon can be changed via the TABS at the bottom of the composition grid. See PVT Project File Structure for a more detailed description of streams. The display shows the Working Composition of the selected Stream. The composition can be viewed and manually changed if required. in common with all grids the blocks of data can be copied to and from the clipboard with standard Control C Control V etc. (see Grid Help) The top section of the display shows the components a,their mole percents and the properties of each component pseudo component or group. The corner of the properties grid gives a coloured message which indicates the status of the composition i.e. GROUPED or MATCHED. When a composition is grouped the components which make up each group can be found by clicking on the component name. Click then on the down arrow which appears. As shown below a subgrid appears containing the names of the grouped components.

The properties listed are: Critical Temperature Tc Critical Pressure Pc Acentric Factor (Omega) Critical Volume Vc Omega A Omega B Molecular Weight Boiling Point Tb Specific Gravity Apparent Density (Rho App) Parachor Volume Shift C Volume Shift S Z Rackett Critical Compressibility Zc Melting Point Heat of Melting Change in Volume at Melting Molar Volume Solubility Parameter of Liquid Solubility Parameter of Solid



The values for pure components normally come from the selected data base. Mixing rules and correlations are used for groups and pseudos. The values within the tables can be edited on this display by clicking within a cell and entering a new number.The Edit Mole Percents dialog should be used to change percentages of components after matching has been done . If no matching has taken place use the Edit Composition Dialog Volume Shift S and Volume Shift C are properties used in alternative methods of calculating Volume Shift. Z Rackett is used in one method to estimate Volume Shift C The third section of the display shows the Binary Interaction Coefficients for pairs of pure components, groups , and pseudos. Again values can be changed within this section. 7.6.1 Control Buttons The control buttons have the following functions.

Exit and Save This option registers the changes made and closes down the display.

Cancel This option shuts down the display and ignores any changes which have been made.

Quick Calc. This option provides the user with access to a subset of the calculation menu as a means of checking the consistency of the entered composition information.

The small calculation display provides the following options: Phase Envelope

PVTP User Guide


7.6.2 OmegaA and OmegaB In the normal mode of operation OmegaA and OmegaB are constants(see Help on Regression with OmegaA and OmegaB). The values are the same for each component and are displayed. The numbers cannot be edited in this mode. However, when a different regression mode is chosen within the Regression Match Data Dialog, the display changes to reflect that the values are now in use. If the Global mode is selected a single value is used for all components and the display looks like this:

In Individual mode each component can have a different value for OmegaA and OmegaB. These values can be edited by the user if required.

PVTP User Guide


7.6.3 Plotting Component Properties

This option brings up the Component Properties Plot. A typical plot would be:

The program automatically creates a stream containg the original database properties. This allows the user to assess the changes which have been made during regression. See Chapter 11 for more information on Plotting

PVTP User Guide


7.7 Grouping This Grouping Options display can be viewed by selecting the Grouping option within the Data menu. Figure 7.8 shows a typical display.

Figure 7.8: Grouping Options

Grouping allows a complex mixture of many components to be represented by a smaller number of representative groups. This operation greatly increases the speed of calculation. Mixing rules are used to give the group properties which represent the combination of the group members. The simplification of the system, however, does bring with it the potential risk of not being able to match fully the complex properties of the real mixture. The stream to be grouped is selected using the stream combo box.. See PVT Project File Structure for more information on streams. The method radio buttons allow the user to choose between two major options: Automatic ( Elf Aquitaine) Method and Manual Method When Automatic Method is selected along with the number of groups , the pure components are sorted automatically into groups. The number of groups required is entered in the edit box provided. The smaller the number of groups the faster the calculation will go. However, if too small a number is used the Equation of State may not be able to match the more complex properties of the mixture, e.g. regression on a particular combination of separator measurements may not find a reliable solution. A choice of 5 groups seems to work for most systems. When streams are to be mixed it may be beneficial to keep the second or injected stream separate during grouping. This can be done be selecting an inject stream and clicking on the Injected Stream checkbox. When a regressed stream is being grouped it is possible to say whether the regressed or basic properties are used in the grouping via the Use Regressed Properties checkbox. Clicking on the Group control button will initiate the grouping and bring up the View Properties display. The Manual Method option in combination with pressing the Group control button brings up the Manual Grouping Display.



NOTE the total group number will be the group number specified in this dialogue + the number of injected stream components. Manual Method Selecting this option and clicking the Group control button passes control to the display shown in figure 7.9. The top of the screen shows the groups defined so far. The bottom half contains two list boxes one for components and another for groups . Groups are created by clicking on the desired components , clicking on the desired group within the list box and clicking on Add Group. Components grouped are removed from the components list box and placed in the table. Delete Group will remove components from the selected group and place them in the components list box. Reset Groups will delete all groups and place all components back in the component list box. When Grouping selection are complete click on the OK button. This action will bring up the Grouping Information display described in section 7.5

Figure 7.9: Manual Grouping

PVTP User Guide


7.8 Reference Data This display can be viewed by selecting the Reference Data option within the Data menu. This dialog shows the Reference Data for the currently active Stream.Each Stream contains its own version of this data (see PVT Project File Structure Section 7.0). The stream can be changed using the combo box provided. Figure 7.11 shows a typical dialog box. Data for Reservoir Temperature, Reference Depth and Static Pressure can be entered for each stream. The Temperature is used to calculate the Saturation Pressure in the small calculations menu and to act as a starting temperature for the compositional gradient calculation. The reference depth is also taken as a starting point for the compositional gradient calculation. The static pressure at depth is used in the compositional gradient and represents the pressure in the reservoir at which the sample has been taken. The second section of this dialogue allows the user to modify the Standard Temperature and Pressure. These variables are used throughout the PVT package to determine the volumetric properties of the oil and gas. Some PVT reports particularily from warmer areas demand values other than the default numbers of 0 psig and 60 degrees F. Although the differences in FVF and GOR are not large , use of the wrong reference conditions can make matching difficult. When the PVT file is saved the Standard conditions used are also saved with it. The Save as Default button will store the values and use them in any new PVT file. These numbers are entered in the units displayed at the right hand side of the box. See Section 3.4 if another set of units is required. Please note that these variables can also be changed by using the Edit Composition display (see Section 7.2 )

Figure 7.10: Reference Data



7.9 Decontamination Where data is limited and the contamination can be isolated as a single pseudo component , the edit mole percents facility can be used. Normally a procedure like that described in Appendix C should be followed. 7.9.1 Edit Mole Percents This option is called via the Data menu. A typical display is shown in figure7:10a.

Figure 7.10a: Edit Mole Percents Dialog

Use this option to: a) Edit the percentages of existing stream components , and b) copy an existing stream and then edit the percentage compositions if required . The display is loaded from the Data|Edit Mole Percents menu option(see DATA MENU) To edit an existing stream : Select the required target by clicking on the tabs beneath the stream list table and click on Edit All Streams. Type in the required percentages up to 100% and press Exit and Save. To create and edit a new stream : Edit the stream name and comment of the next stream. Select the stream from which the copy is to be taken by clicking on the tabs beneath the stream list table. Press on the Copy Stream Button to create the new stream. type in the required percentages up to 100% and press Exit and Save. A copied stream carries all the data with it from the target stream i.e. component properties , reference data , match data etc.

PVTP User Guide


NOTE: 1) If the stream being copied is grouped the new stream will become one with only pseudo components , each group being replaced by a pseudo with the same properties. This is required as no information is available to the program on how the new percents should be spread across the components making up the group. 2) When a composition is grouped, the components within each group can be seen by clicking on the group name and clicking on the dropdown box arrow that appears. Clear will remove all percentages from a selected stream if editing is available for that stream ( the background colour is white) See also: PVT PROJECT STRUCTURE. -where streams fit in to the overall data structure (Ch.7.0) SELECT COMPONENTS - this display has an option to add an empty stream(Ch.5.5) ADD STREAM - copies existing streams or imports streams from other files(Ch.7.2) 7.9.2 Decontamination Control Dialog This display is called by the main display via the Data|Decontamination menu option. See theDecontaminate procedure(Appendix C) on how the file should be prepared prior to using this facility. A typical display is shown in figure7:10b

Figure 7.10b: Decontam. Control Dialog

The main table shows the components and the expansion of the pseudo components. The colours indicate the components which are calculated to make up each pseudo. The distibution of the the pseudo split components is determined by the path taken in characterising the pseudo within the Pseudo Properties Dialog and the Advanced Splitting Dialog which is accessed from it. The correct setup of this split and the matching of the fluid must be done prior to using the decontamination feature.



The split method indicated above the table is the key to the shape of the pseudo component distribution. This can be selected within the advanced splitting dialog. An important split option in decontamination is to follow a profile.A profile would be contaminant-rich part of the extended sample component distibution (C12-C20). Using this method a profile can be created within the Split Profile Creation Dialog. This display is entered by a stream with a fixed pseudo distribution and a set of pseudo properties which characterise the fluid.THe program splits out the composition and the main properties used by the EoS i.e. Tc,Pc,Vc,AF,BPt and the SG. The initial display would be as follows:

Figure 7.10c: Decontam. Control Dialog

The user must now give the program a new values for the important components i.e. where the contamination was at its worst. Type the new values into the New Mole% column. Alternatively, values can be transferred from the clipboard using the standard Contol + V combination. To get an idea what result the decontamination process will produce click on the QuickLook button.

This option does the decontamination to a temporary stream and brings up the QuickLook Selection Dialog.

PVTP User Guide


To carry out the decontamination proper click on the Decontamination button.

The user will now be given the option (via the Mode Selection Dialog) of copying the results of the decontamination to the existing stream or to a newly created one. The decontamination calculation proceeds as follows:

The individual component mole percents are set equal to the New Mole% values , where defined. The remaining component mole percents are adjusted to make up the 100% total

and to follow the trend of the original values. The new full composition appears as the Cald. %. The Calcd% are used in conjunction with the initial properties to generate a new set

of properties for each component and a combined version for each of the pseudo components. The pseudo component start and end values can be seen by clicking on the View/Change button.

The trend in the individual compositions can be seen by using the Plot button. The Clear button erases all the New Mole% values.



7.9.2.1 Decontamination Mode Selection Dialog See also Decontaminate Procedure(Appendix C) This display is called via the Decontamination Control Dialog. A typical screen is shown below:

The options are to do all the operations in the existing stream or to create a new one. If a new stream is to be created the stream name and comment can be edited at this stage. Press Exit and Save to carry out the decontamination and return to the control dialog. 7.9.2.2 Decontamination Quick Look Dialog See also Decontaminate Procedure(Appendix C) This display is called via the Decontamination Control Dialog. A typical screen would be:

As part of the quick look procedure the program creates a temporary stream and does the decontamination procedure within this stream. This dialog allows the user to see the results of this process as a table of component properties by clicking on View Properties. Alternatively, the standard quick calc dialog can be called by clicking on the Quick Calc button.

PVTP User Guide


7.9.2.3 Decontamination Pseudos Dialog See also Decontaminate Procedure(Appendix C) This display is called via the Decontamination Control Dialog. A typical screen would be:

When the decontamination screen is entered and exited , the program stores the properties of the pseudo components at this time. These values are then taken as the reference for any futher decontamination calculations. When decontaminate is pressed within the control display , the program looks to these values to set compositions and properties. It is for this reason that the decontamination screen should only be activated after the fluid is fully matched The top table shows these reference values. The bottom table gives the current working pseudo component numbers. These would normally be the result of the decontamination operation. If ,however, it was found necessary to do further work on the undecontaminated fluid, and the user wishes to change the stored reference values,this display allows the user to overwrite the archived values with the working set by clicking on the Copy button.

PVTP User Guide


7.10 Match Data This series of displays allows the user to enter PVT laboratory measured data for matching. on a stream by stream basis. Each Stream holds its own separate set of data points.(see PVT Project File Structure) The stream being acted upon can be changed using the combo box provided. After supplying the data,the system individual or grouped properties can be then be adjusted using non-linear regression techniques (using the Regression option from the Data menu) to best fit the measurements. This combination represents a powerful technique for adjusting the idealised equation of state to mirror the real world. The Matching option is invoked by selecting Enter Lab Data within the Data menu.

Figure 7.11: Match Table: Multi-stage Separator

Match data tables are available for the following measurements: Saturation Pressure(PSAT) and critical temperature Constant Composition Expansion(CCE) Constant Volume Depletion(CVD) Differential Liberation(DIFF) Separator Data(Sep) Compositional Gradient(CmpGrd) Swelling Test(Swell) Wax Appearance Temperature(WAT) Wax Amount(%SOLID) For each match data table, enter the required information.The PVT Step by Step guide gives recommendations and examples of what data should be used. A reference temperature is required for CCE, CVD match data.The program will prompt for any missing information With CVD only on temperature is required, the program will automatically copy this information to each row. Unlike previous versions the CCe calculation can now be done at multiple temperatures.



When the Compositional Gradient table is selected the reservoir reference conditions are shown in read only form. Adjustment of these values is available using the Reference Data option within the Data Menu.

The grid tab buttons shown above allow the user to move between the match input tables. The tabs also indicate which tables contain data. Tables with data have coloured tabs. Important Note on Differential The calculation of GOR and FVF for a differential liberation is done with respect to residual volume.In order that this volume can be determined all the steps must be added as in the example below

PVTP User Guide


SOLIDS Note that the grids which contain Wax Options are at the end of the scroll bar and must be scrolled along to:

INCLUDE/EXCLUDE Any data point or groups of points can be excluded from the regression process.Simply highlight the desired points and press exclude.Excluded points areindicated by a GREY text background colour. To include points highlight again and press include. This feature can be very useful with liquid dropouts. Enter all values, exclude all and select values as required for inclusion. WEIGHTING Any data point or groups of points can be given a different weighting between high 10 and low 1.This will affect how the regression algorithm responds to the error generated by this point. This weighting is combined with the process weighting (high,medium,low) available within the regression display to give an overall value.To change a weighting,select a point or group of points, change the weighting value and press Set Weighting. Weightings of less than 10 are indicated by the point having a BLUE text colour GRID ASSIST SUB DIALOG Place the cursor anywhere in the table and press the right hand mouse button. A small dialog will appear as shown below:



The Reset button causes the user to be prompted to select if the displayed table or all matching tables should be zeroed. Note that the cleared table or tables will not become part of the project until OK is also selected. The Plot button brings up a display of the entered data where applicable. Clicking on OK registers any changes which may have been made and closes down the display. Cancel will close the display ,loosing any data which may have been entered. NOTE 1: Oil Viscosity can be selected as a match variable within the CCE Table. NOTE 2 the Oil FVF within the multi-stage Separator calculation. is corrected through all the succeeding stages.This correction can add up to 10 % to the un-corrected value. To activate the correction add all stage temperatures and pressures to the match table,even if no other matching is done within the lower stages. NOTE ON GRIDS In common with all grids within the program the grids displayed can be copied from and to using standard widows editing keys. 7.10.1 Matching on Mixture Critical Temperature Matching on crtical temperature is available on the first line of the PSAT This option is intended to help with difficult fluids where the phase is problematic to reproduce with the Equation of State. A measure of phase is the position of the critical point within the phase envelope. If the reservoir temperature is left of the mixture critical temperature the fluid is an oil. If right, the fluid is a gas. If the critical point does not exist the fluid is assumed to be a gas. This match point allows the user to push the critical point in the desired direction. One not uncommon use is where a condensate shows up as an oil at the start of regression. Initially the fluid below shows up as an oil. The reservoir temperature is 200 deg F but the mixture critical temperature is 500 deg F

To help the situation enter a target value of 180 for the Tc within the PSAT Match Data Table. An important option to use for this type of application is the checkbox which prompts the program to assume that the non detection of the critical point is taken as the target being reached. This means that if the critical point disappears the temperature will be set as the target of 180 giving an error for this calculation of zero. The disappearance of the critical point is not uncommon with HTHP condensates.

PVTP User Guide


Select the Critical temperature within the Regression Match Data dialog.

Regression produces the following beneficial result. There is no critical point and the fluid is now a condensate.



7.11 Regression This option is made available when PVT laboratory data has been entered for matching (see section 7.8) The option is invoked by selecting Regression within the Data menu and is used to perform the non-linear regression which adjusts the compositions and properties to best fit the laboratory measured PVT data. The non-linear regression matching technique can be used on up to six PVT match tables, MODEL Three model options can be selected within the program VIZ 1) Original - This model makes all component Pcs, Tcs and Acentric Factors available for regression. When selected this model allows the user to also limit the movement of the selected properties via the checkbox which becomes visible. When invoked this option restricts the movement of all properties such that the progression with molecular weight remains reasonable. Component property values can be plotted within the View Properties Dialog. It should be noted that limiting property movement will inevitably reduce the flexibility of the EoS method and may decrease the accuracy of the final match with some fluids. 2) Global OmegaA and OmegaB. This will use one value of each variable for all components. In addition, the pseudo component and grouped component Tcs Pcs and AFs will be available for regression. See help on Regression with OmegaA and OmegaB for more details. 3) Individual OmegaA and OmegaB. This will use an individual value of each variable for every component. In addition, the pseudo component and grouped component Tcs Pcs and AFs will be available for regression. See help on Regression with OmegaA and OmegaB for more details. The Reset Omega A and Omega B Values button that appears with models 2 and 3 will set these values back to their default EoS levels. each with different characteristics. MODE The program has two modes for Equation of State regression : Single Stream Multi-stream

The mode is changed by way of the radio buttons at the top of the dialog. SINGLE STREAM MODE The initial regression display is shown in figure 7.12.

PVTP User Guide


Figure 7.12: Regression: Match Selection

As the name implies this mode regresses only one stream i.e. the component properties of one stream are changed to match its Lab Data. The stream being manipulated is selected by clicking on the tab containing the stream name. The tab background colour is changed to BLUE if any selections have been made for the stream.(see STREAMS Chapter 5.5) This display highlights all the variables available for regression . Choose a variable by clicking on the checkbox alongside the name. The total selected is shown on the right of the dialog The variable can then be set at high ,medium or low contribution to the overall regression calculation. All selections for the selected stream can be removed by clicking on the Clear This Stream button. It is not necessary to select all variables, especially in cases where data may be suspect. The High, Medium and Low radio buttons allow the user to adjust the weighting given to each selection. See also Lab Data Entry Dialog for more information on weightings. When selection is complete click on the Regress control button. This action will bring up the Regression Parameter Selection Dialogue. Main closes down the dialogue,saving all changes Cancel closes down the dialogue,ignoring all changes MULTI-STREAM MODE

Figure 7.12a: Regression: Match Selection



This mode is designed for projects where multiple samples and corresponding PVT data is available from the same reservoir.This may be from wells at different depths or surface/reservoir samples. The fluid components are generally the same but the compositions and therefore the measured characteristics are different. The principle is to match all the data with one set of component properties. Each stream (see STREAMS Chapter 5.5) represents one sample with its own composition and Lab Data. All the stream component properties will end up the same,but the initial set will be taken from the master stream. This can be changed using the combo box provided. Selection is carried out in the same way as descibed above for a single stream. As selections are made the Stream Summary shows the number chosen for each stream. A running total of choices is provided. Note that a maximum of 25 selections is available. The Clear All Streams button will set all stream selections to zero. Stream Selections can be individually cleared by clicking on the name or names within the Stream Summary and pressing on the Clear Selected button. When selection is complete click on the Regress control button. This action will bring up the Regression Parameter Selection Dialog.

PVTP User Guide


7.11.1 Regression Parameter Selection Dialog The component selection displayed depends on which regression model was selected within the Regression Match Data dialog (section 7.10). ORIGINAL MODEL If not regressing on viscosity, for each group or component , the user can select whether to regress on any or all of the following: Critical Temperature Tc Critical Pressure Pc Critical Volume Vc Acentric Factor AF Volume Shift C or S

In addition for solids (see Section 7.10.4) the following properties are added: Melting Point Heat of Melting

A typical display shown in figure 7.13.

Figure 7.13: Regression: Match Selection

This display is called by the Regress Option in the Regression Match Data dialogue. For each group or component , the user can select whether to regress on any or all of the Our latest methodology for parameter selection is given in What Properties to use in Regression (Section 7.10.2) The matching of viscosity requires a particular procedure which is described in Matching Viscosity (Section 7.10.3)



Since the Binary Interaction of the lightest and heaviest components are important , it is also possible to regress on the Binary Interaction Coefficient of them. Five Binary Interaction Coefficient options will be provided when available. GLOBAL OMEGA A AND OMEGA B MODEL With this model a single value for Omega A abd Omega B are applied to all components.The values are displayed within the grid. A Checkbox is supplied to select each parameter. Clicking on Reset at the top of the column will set the respective omega parameter to the EoS default value. In this mode the Tcs, Pcs and AFs of the pseudo and grouped components can also be selected. In all models the volume shift parameters and BICs are selectable See Regression with OmegaA and OmegaB (section 7.10.6).

INDIVIDUAL OMEGA A AND OMEGA B MODEL With this model a each component has its own value for Omega A and Omega B. A Checkbox is supplied to select each parameter for every component. Clicking on All at the top of the column will set on all the respective omega parameters. None will switch them off. In this mode the Tcs, Pcs and AFs of the pseudo and grouped components can also be selected. In all models the volume shift parameters and BICs are selectable. See Regression with OmegaA and OmegaB (section 7.10.6).

PVTP User Guide


7.11.2 Volume Shift When an equation containing the Volume Shift option is used, the parameter list expands to contain the appropriate shift parameter ( see Volume Shift Help). A volume shift control panel is also included. 7.11.3 Control Buttons The control buttons have the following functions: OK This option stores the values entered (in memory , not on disk) . and closes down the display. Cancel This option shuts down the display and ignores any changes which have been made. Regress This option starts the regression process. When complete, the Regression Information screen is automatically displayed. See the note on regression below. Results This option displays the Regression Information screen. See the note on regression below. All ON This button sets all the available regression options.



All Tc,Pc,Vc,AF,C or S Shift This button sets all the variables within the column on. (see also Mouse Shortcuts) No Tc,Pc,Vc,AF,C or S Shift This button sets all the variables within the column off.(see also Mouse Shortcuts) Clear All This button switches off all the available regression options. 7.11.4 Mouse Shortcuts The programmed has been designed to give quick access to a row of options.Clicking on the omponent name in various ways sets data on and off. The options are: left mouse button - switch on AF Tc and Pc right mouse button - switch on all properties shift key and left mouse button - switch off AF Tc and Pc shift key and right mouse button - switch off all properties 7.11.5 Separator The Separator data option mirrors the feature available within the individual calculation sections. The user can define a separator train through which the oil produced within CCE, GRAD etc. will be flashed to correct the Oil FVF and GOR. The processes which are used to return an oil to standard conditions can significantly change the final oil characteristics and the amount of gas liberated on the way. All stages do not need to be entered and a last flash to standard conditions is always included. The checkbox within the separator area switches the correction on and off. Setup brings up the small dialogue where the separator conditions are defined.

PVTP User Guide


7.11.6 What Properties to Use in Regression Our recommendations for which variables to use have changed with our experience of a wider and wider variety of fluids. We now generally start with all Tcs and Pcs selected (except for N2 and CO2). If BI coefficients are available select the value between C1 and the heaviest component. The reason AFs are not chosen initially is that they have a tendency to be pushed to extreme values which in turn lifts the low temperature end of the Phase Envelope to near vertical. Using Tcs and Pcs give a gentler and more controlled path to a solution. If using Tcs and Pcs does not result in convergence, start adding AFs. If Volume Shift is required select some Si or ci component properties. Please note that Volume Shift is not recommended until no other combination is found to work( see Volume Shift Chapter 4 for more details) See also Step by Step Guide (Apendix A) A typical starting display would be that in figure 7.13: There may be some objections to using the properties for pure components below C6 since they are measurable. We have found the above method to work universally. however, we do not prevent the user from selecting any combination of properties or approaching the solution differently. It is our contention that the pure properties are being used within an empirical equation with arbitrary methods of calculating and mixing the constants which are derived from them (see EoS Help). This suggests that any purist approach will only limit getting a result not make it better. The quotation below makes the same point. Quotation from Molecular Thermodynamics of Fluid-Phase Equilibria by J Prausnitz and R. D. Lichtenthaler. "Many equations of state have been proposed and each year additional ones appear in the literature,but most of them are either totally or at least partially empirical. All empirical equations of state are based on more or less arbitrary assumptions which are generally not valid. Since the constants which appear in an empirical equation of state for a pure gas have at best only approximate physical significance, it is very difficult ( and frequently impossible) to justify mixing rules for expressing the constants of mixture in terms of the constants of the pure components which comprise the mixture.As a result,such relationships introduce further arbitrary assumptions and it has been found that for typical empirical equations of state, one set of mixing rules may work well for one or several mixtures but poorly for others." 7.11.7 Matching Viscosity In the Equation of State model ,viscosity is calculated by a range of methods. The default method is Lohrenz, Bray and Clark (LBC).See Viscosity Models for more details of the models available. The LBC model is default as it the only model in general use within other programs. Only one model is active in a file at any one time. The active model is selected via the combo box which appears on the regression selection display.



REGRESSION WITH LBC This method uses composition , specific gravity and , more importantly, critical volume to get the value for viscosity(see help on LBC model). Critical Volume (Vc) is the property which is used in the viscosity regression. The key to understanding the procedure outlined below is the fact that, although LBC viscosity is dominated by Vc, in all other calculations the property has little on no effect. The matching of viscosity can be effectively de-coupled from the total fluid matching exercise. The procedure to adopt is as follows: 1. Set up and carry out the fluid matching for all variables except viscosity eg.

PSat,PSat density, separator GOR , Stock Tank density etc. Suggestions for the variables to use are given in the Step by Step Guide. See also What Properties to use in Regression.

2. Enter the viscosity values to be matched to using the CCE table within the Match

Data Tables. Please note that there are limitations to what the LBC method can do (see NOTE below).

3. Within the Match Selection Dialog ,click on the viscosity or viscosities to be

matched. This action will switch off all non-viscosity selections (psat etc. ). A typical display would be:

Figure 7.14a: Regression: Match Viscosity

4. Click on Regress to bring up the Parameter Selection Dialog . No Selections will be

available other than component Vcs. Select all the Vcs using the Vc All button. A typical display would be:

PVTP User Guide


Figure 7.14 b: Regression: Match Viscosity

5. Click on Regress to match viscosity. 6. Return the matching system to the selections prior to step 1 i.e. PSat etc and Tc Pc

AFs selected. Regress again .This step is not really necessary as the matching should not be disturbed. The operation does ,however ,reestablish the selections which made the overall match possible.

NOTE on LBC The LBC is the best compositional correlation for viscosity that we have tested to date. It does ,unfortunately, have some limitations of which the user should be aware. The values calculated for oils ,without matching, are generally not very good and can sometimes be wrong by an order of magnitude. This limitation is counteracted to a great extent by the Automatching of Viscosity feature. Unfortunately,another problem arises from the inflexibility of the algorithm. With heavier oils it can be difficult to get a full match from reservoir pressure to surface. If this occurs and the output is to be in the form of Black Oil tables(Section 3.1) it may be better to match the viscosity within Prosper or MBal using Black Oil correlations. REGRESSION WITH MODELS OTHER THAN LBC Unlike LBC which uses Vcs, the other viscosity models use Tcs,Pcs and liquid densities to calculate viscosity. Matching directly on these properties would destroy the match to the main fluid properties such as saturation pressure and separator GOR. As an alternative, these models have been given a shift and multiplier mechanism to improve the match. After matching the viscosity becomes: Visc = Visc*Multiplier + Shift The procedure to match becomes: 1. Set up and carry out the fluid matching for all variables except viscosity eg.

PSat,PSat density, separator GOR , Stock Tank density etc. Suggestions for the



variables to use are given in the Step by Step Guide. See also What Properties to use in Regression.

2. Enter the viscosity values to be matched to using the CCE table within the Match Data Tables.

3. Within the Match Selection Dialog ,click on the viscosity or viscosities to be matched. This action will switch off all non-viscosity selections (psat etc. ). A typical display would be:

Figure 7.14 c: Regression: Match Viscosity

4. Click on Regress to bring up the Parameter Selection Dialog . No component

selections are available. A typical display would be:

Figure 7.14 d: Regression: Match Viscosity

5. Click on Regress to match viscosity. The shift and multiplier parameters are

displayed. Gas and Oil values are matched separately. The Reset Params button can be used to undo any matching that has taken place.

6. Return the matching system to the selections prior to step 1 i.e. PSat etc and Tc Pc AFs selected. Regress again .This step is not really necessary as the matching

PVTP User Guide


should not be disturbed. The operation does ,however ,reestablish the selections which made the overall match possible.

7.11.8 Regression With Solids In the Equation of State model ,viscosity is calculated by the method of Lohrenz, Bray and Clark (LBC). This display is called by the Regress Option in the Regression Match Data dialogue. if a Solid option has been entered in the Match Data Tables. The possible entries include Wax Appearance Temperature and Amount of Wax. If either of these option is chosen the display expands to include two further columns as shown below:

Figure 7.15: Regression: Solid Properties

From the expressions within Wax Modelling and Wax Model Details it can be seen that the important variables as far as solid formation are concerned are Melting Point and Heat of Melting. Since a component is only allowed into the solid if its melting point is greater than the test temperature only the heaviest components have any effect. Melting Point is the key variable and it should be used first. Heat of Melting has little effect on Wax Appearance Temperature but it significantly changes the percentage of wax produced. The lack of significant properties to change and the inflexibility of the underlying correlations may mean that the model cannot fully match the variability found in complex wax forming fluids.



NOTE: From the models it is obvious that the other component properties used in regression i.e. Tc,Pc,AF etc. do not significantly influence solid formation.Their effect comes in the composition and fugacity of the liquid solvent. It is therefore possible to match solid formation in isolation from the other match points eg PSAT in a similar way to that proposed for matching viscosities. The procedure to adopt is as follows: 1. Set up and carry out the fluid matching for all variables except solids eg. PSat,PSat

density, separator GOR , Stock Tank density etc. Suggestions for the variables to use are given in the Step by Step Guide. See also What Properties to use in Regression.

2. Enter the Wax values to be matched to using the WAT and %Solids tables within

the Match Data Tables. 3. Within the Match Selection Dialog ,switch off all selections (psat etc. ) except solids.

A typical display would be:

Figure 7.16: Regression: Solid Properties

4. Click on Regress to bring up the Parameter Selection Dialog . Use the Clear All

button to remove the Tc,Pc AF etc. Selections. Select the component Melting Points and if necessary Heats of Melting (as above)

5. Click on Regress to match wax properties. 6. Return the matching system to the selections prior to step 1 i.e. PSat etc and Tc Pc

AFs selected. Regress again .This step is not really necessary as the matching should not be disturbed. The operation does ,however ,reestablish the selections which made the overall match possible.

PVTP User Guide


7.11.9 Model Selection

A combo box allows the user to select between the various wax models.Clicking on the Reset Props button resets the important component properties back to the default values outlined by the model's author. WARNING using this button will reset any solids regression that has been done. See Wax Modelling (Chapter 4) for more details on the model types available. See Lab Data/Matching (Section 7.9) for more details on what can be matched for solids. 7.11.10 Notes on Regression Due to the large number of calculations , regression can be a slow process, even when using a fast computer. During the regression process the computer will display the elapsed time, the number of iterations to date , the best and latest error (Chi) found. A cancel dialogue also allows the user to stop the process and use or discard the results at that point. If allowed to complete the regress option automatically brings up the Regression Results Display(same as Group Properties) If the calculation completes due to the number of regression cycles and a satisfactory error has not been achieved , it is possible to regress again with the composition set at the regressed value. NOTE 1 the maximum number of regression cycles completed before an automatic stop can be adjusted using the Preferences|Calculation Tolerences menu option. NOTE 2 the Oil FVF within the multi-stage Separator calculation. is corrected through all the succeeding stages.This correction can add up to 10 % to the un-corrected value. To activate the correction add all stage temperatures and pressures to the match table,even if no other matching is done within the lower stages. If no satisfactory regression can be achieved the problem may be within the following: 1) Incorrect or incompatible data entered for lab matching 2) Too few groups used to give the system flexibility to match see Grouping 3) Composition setup particularly of pseudos not adequate for matching The regression may succeed if a different path is taken to the solution e.g. by 1) Taking each calculation consecutively i.e. regressing on one calculation then using the regressed values as input to the next. A reasonable order is Psat, followed by CCE then Separator etc.



2) Selecting a different BI Coefficient correlation or entering new values manually. Most calculations are very dependent on the value of coefficient between the lightest and heaviest components. 3) Taking care to match the Pseudo properties to the best lab measurement available. 4) Selecting a different set of properties to regress e.g. density is sensitive to Pc,Tc values while viscosity(see CCE matching) is almost totally dependent on Vc. 5) Increasing the number of groups or ungrouping completely as this gives the calculation more flexibility. NOTE 3 the matching of viscosity using the Lohrenz-Bray-Clark method requires a particular procedure which is described in Regression - Matching Viscosity (Section 7.10.3) 7.11.11 Regression with OmegaA and OmegaB Within the 2 most common Equations of State i.e.. Peng Robinson and Soave Redlich Kwong OmegaA and OmegaB are empirically derived constants . How these variables fit into the overall equation is given in the help on Acentric Factors. In the Peng Robinson(PR) equation the a(T) function at the critical point is given by the empirical relationship

)(4572422

C

C

PTR

)(C

C

PRT

.0)( cTa =

The constant 0.45724 is the OmegaA parameter. In addition the repulsive factor b within PR is given by:

0778.0b =

The constant 0.0778 is the OmegaB parameter. The equivalent values for the Soave Redlich Kwong(SRK) equation are 0.427 for OmegaA and 0.08664 for OmegaB. A methodology has developed within the industry to treat OmegaA and B as variables for use within the matching process. This is really an alternative to using individual components Tc and Pc properties. One advantage of this approach is that it leaves measured properties such as the Tc and Pc of methane untouched while giving additional parameters to match with. This methodology is particularly important if a corresponding states model for viscosity or thermal conductivity is to be used. One problem which may arise with going this route for regression is passing the match on to other programs. Some compositional exports do not contain OmegaA and OmegaB terms eg Prosper. In addition, with some fluids this approach will not give as complete a match as using individual Tcs and Pcs. There are 2 versions of the OmegaA and OmegaB match available within the program: 1) Global - the same value for OmegaA and OmegaB are used for all components and 2) Individual - each component can have a different value for OmegaA and OmegaB. The regression model is chosen within the Regression Match Data Dialog using the listbox provided:

PVTP User Guide


Selecting mode 2 or 3 will change the options within the Regression Parameter Selection Dialog and also within the View Properties Dialog. 7.12 Plot Test Points This feature has been added to help the user compare Lab or other experimental data with the curves generated by plotting the results of the various PVT EOS calculations. Access to the input screen, shown in figure 7.17, is gained when either a) the Enter Plot Test Points option within the Data menu is selected or b) the Set Test Pts. button is clicked within an EOS calculation plot.

Figure 7.17: Test Point Input Table

The table allows the user to configure up to 100 points. Entries are defined by setting up a calculation and column name for each or a group of points. If the point matches the variables and range of a calculated plot the Test Points will be drawn in the same way as match data is done. The points can be defined in any pattern and ordered using the Sort Table option. The table is automatically sorted when this dialogue is first displayed. To define test points follow the following procedure:



PVTP User Guide

1) The first step in this process is to select a row or range of rows. This is done by clicking on the raised row number at the start of the row. Adjacent rows can be selected by holding down the mouse button and dragging the cursor across multiple row numbers. 2) Once selected the rows can be setup,cleared or the data only erased.

3) When the rows have been selected ,choose a calculation and a pair of variables.The click on the Setup Rows button . The program will setup the calculation type , X and Y variable names and units within the grid. 4) Enter the test data in the X Value and Y Value columns 5) Click on Exit and Save when all selections have been made Display of the test points can be toggled on and off with the Show Test Points on Plot checkbox. Clear Rows This option removes any definitions or data within a selected area. Clear Row Data This option removes data within a selected area but leaves the calculation and variable definitions intact. Clear All This option removes all definitions and data from the table. Exit and Save This option closes down the dialogue with all the changes saved Cancel This option closes down the dialogue with all the changes abandoned. If any test points are detected which match a Plots variables and range thay are automatically plotted (see figure 7.18).



Figure 7.18: Test Points within Plot

8 Calculation EoS This section describes the calculation input required for the Equation Of State PVT model and the various forms of results. Calculations can be initiated in three ways I. by selecting an option from the Calculation section of the main menu II. by clicking on one of the calculation icons within the main toolbar III. by clicking on the Calculate control button within the Edit Composition and Properties

displays (see Chapter 7) Methods I. and II. give a choice of the following :

◊ Calculate Critical Pressure and Temperature (section 8.1) ◊ Calculate Phase Envelope for a range of Vapour Fractions(section 8.2) ◊ Calculate a range of Saturation Pressures(section 8.3) ◊ Calculate the results of a Constant Composition Expansion (section 8.4) ◊ Calculate the results of a Constant Volume Depletion (section 8.5) ◊ Calculate the results of a Depletion Study (section 8.6) ◊ Calculate the results of a Differential Expansion (section 8.7) ◊ Calculate the results of a Separator Process (section 8.8) ◊ Calculate the results of a Compositional Gradient (section 8.9) ◊ Calculate the results of a Swelling Test(section 8.10) ◊ Calculate the results of a Slim Tube Simulation(section 8.11)

Where applicable ,the last set of entries for each calculation are saved with the other data in the PVT project file. Method III. provides the user with access to a subset of the calculation menu as a means of checking the consistency of the entered composition information. The small display provides options to calculate (section 8.12):

◊ Phase Envelope ◊ Critical Point (Temperature and Pressure) ◊ Saturation Pressure (at the reference temperature) ◊ Flash to Standard conditions ◊ Flash Through Separator Stages ◊ Maximum water in Hydrocarbon Phase

All calculation results are retained for inclusion in the Reports available with the PVT package (Chapter 9)


8.1 Critical Point Calculation

A critical point calculation can be initiated by selecting the Critical Point option from the calculation menu or clicking on the icon shown above. Alternatively , the Calculate option on the Edit Composition Screen etc. can be used (see section 8.12). The result of the calculation is given in a dialog box . Figure 8.1 shows an example of this type of output. Contained within the display are values for • Critical Temperature Tc • Critical Pressure Pc • Critical Temperature Tc • Critical Volume/Gas Constant Vc/R • Critical Compressibility Zc • Number of Iterations In addition indication is given of the kind of system at reference conditions i.e. Dew Point (gas) or Bubble Point (liquid)

Figure 8.1: Critical Point

It should be noted that the Critical Point may not always be resolvable for complex mixtures. If this proves to be the case try adjusting the values of Binary Interaction Coefficient , Acentric Factor of the heaviest components and the properties of any pseudo components which have been defined. Remember that the equation of state is not predictive , if a match point is available, always use this to guide your changes.

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Chapter 8 - Calculation EoS 3 -55

8.2 Phase Envelope

A Phase Envelope calculation can be initiated by selecting the Phase Envelope option from the calculation menu or clicking on the icon shown above. Alternatively , the Calculate option on the Edit Composition Screen etc. can be used (see section 8.10). A Phase Envelope calculation can be initiated by selecting the Phase Envelope option from the calculation menu or clicking on the icon shown above. Alternatively , the Calculate option on the Edit Composition Screen etc. can be used. The display below shows an example of the phase envelope input parameters screen. As the display loads it automatically calculates the phase envelope for vapour fraction 1.0. and the currently active stream.(see PVT Project File Section 7.1).

The display is made up of several sections: Stream Selection The list box allows the user to select any combination of streams to calculate. Vapour Fraction There are 2 modes of entry

PVTP User Guide


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1) Auto- the entry boxes are loaded with values of 0.5,0.6,0.7,0.8,0.9, and 1.0 2) Manual entry - Eight entry boxes are provided for entering vapour fractions from 0.1 to

1.0 The CLEAR button will remove all entries in Manual Entry mode. Calculation Limits Entry boxes are provided to change the following values used to limit the phase envelope calculation. Pressure Step - dictates the gap between pressure movements used to detect phase envelope Min Pressure - sets the bottom limit of the calculation Max. Pressure - sets the upper limit of the calculation Integration Step - dictates the size of movement of the Integration function Max. Integration Step - dictates the maximum size of movement of the Integration function Plot Area This shows the shape of the phase envelope calculated . No adjustments are available for this plot. However , the graph can be enlarged and then manipulated by using the Expand Plot button. Status Area This shows the critical points calculated during the phase envelope calculation and also includes a status message area which indicates the progress of any calculations. Note that the Critical Pressure Pc, Critical Temperature Tc ,Cricondenbar ,Cricondentherm etc. may not always be resolved for complex systems. Control Button Area

Included in this area are a series of control button which have the following functions: Exit This option stores the values entered (in memory , not on disk) and closes down the display. Calc. This option recalculates the phase envelope(s) using the latest inputs. Expand Plot This option brings up a full-sized plot of the phase envelope. Set Test Points This option calls the Test Points display. This allows the user to enter ten values for Saturation Pressure versus Temperature. The values will be displayed on the Phase Envelope plot as Match Point crosses Results This option brings up the results dialog as shown below. The user can view all the stream phase envelope data by scrolling down the tables and moving between the tables by way of the stream tabs.


The results can be copied to the Clipboard or to another package such as EXCEL by highlighting the values required and pressing Ctrl + C. Ctrl + V will insert the values into the target program.

Help This option brings up the on-line help. Use of Streams The option of calculationg multiple curves is a very powerful aid in the analysis of petroleum mixtures. Since streams can be filled with varying compositions changes in fluid characteristics can be visualised. For example the program can illustrate how a fluid changes as a result of a compositional gradient. Stream 1 and 2 can contain the compositions of gas

PVTP User Guide


and oil calculated before and after the gas cap has been detected. The phase envelopes are very different but they intersect at the gas cap temperature and pressure. The compositions


8.3 Ranged Saturation Pressure

A Range Saturation Pressure calculation can be initiated by selecting the Saturation Pressure option from the calculation menu or clicking on the icon shown above. This dialogue is used for Automatic and User Selected Input . The automatic version looks like this: Figure 8.4: Range Saturation Pressure Automatic Mode

The user selected version replaces the ranged input with a series of entry boxes which can be used to enter any temperature.

PVTP User Guide


Figure 8.5: Range Saturation Pressure Manual Entry

Stream Selection

The list box allows the user to select any combination of streams to calculate.See PVT Project File Structure for more information on streams. This display contains radio buttons which allow the user to swap between User Selected and Automatic modes. In addition, data entry boxes are provided for entering the limits of the temperature and pressure ranges to be covered and the number of points to be calculated for each variable. The points will be spread evenly throughout the temperature and pressure ranges selected. All boxes should have an entry before proceeding to the Calculation Dialogue.

To bring up the calculation dialogue click on the Calc control button.


Clear removes any entered values

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Volume Shift A volume shift control panel is proved to allow the user to setup and to switch on and off this feature prior to calculation . See Volume Shift and Volume Shift Setup help for more details.

8.4 Constant Composition Expansion (CCE)

A CCE calculation can be initiated by selecting the Constant Composition Expansion option from the calculation menu or clicking on the icon shown above. Constant Composition Expansion is a flash process where all the products are retained i.e. the total amount of each component at the initial conditions is the same at all the measured values, only the phase splits (K values ) have been changed. Separator Data The CCE input displays contain a section for Separator Data. This allows the user to define a separator train through which the CCE liquid will be flashed to correct the Oil FVF and GOR. The processes which are used to return an oil to standard conditions can significantly change the final oil characteristics and the amount of gas liberated on the way. When multiple samples are being analysed, it may be necessary to have individual separator settings for each stream. In this case, the individual radio button should be clicked on. The stream separator settings can be accessed via the tabs at the bottom of the table.All stages do not need to be entered and a last flash to standard conditions is always included.The checkbox within the separator data area switches the correction on and off. The values within this separator data area are loaded and stored separately from those within the Separator calculation. The Copy Sep button will copy the stages from the Separator Calculation (section 8.8) into the Separator Data area.The Clear button removes all values from within the Separator Data area. The calculation input screen comes in two forms viz. Automatic (figure 8.7) and User Selected Entry (figure 8.8).

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Figure 8.7: Constant Composition Expansion Automatic Mode

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In the User Selected version the ranged input is replaced by a grid where any mixture of pressures and temperatures can be entered

Figure 8.8: Constant Composition Expansion Manual Entry

Stream Selection

The list box allows the user to select any combination of streams to calculate. See PVT Project File Structure for more information on streams. This display contains radio buttons which allow the user to swap between User Selected and Automatic modes. In addition, data entry boxes are provided for entering the limits of the temperature and pressure ranges to be covered and the number of points to be calculated for each variable. The points will be spread evenly throughout the temperature and pressure ranges selected. All boxes should have an entry before proceeding to the Calculation Dialogue. Viscosity Method Various viscosity models have been introduced into the PVTp program (see Section 4.6).

PVTP User Guide


Only one model is active in a file at any one time. The active model is selected via the combo box which appears on all the calculation input and regression selection displays.



Clear removes any entered values Volume Shift A volume shift control panel is proved to allow the user to setup and to switch on and off this feature prior to calculation . See Volume Shift and Volume Shift Setup help for more details. Analysis For each calculation carried out, the analysis display presents information on compositions K values,gas and oil gravities etc. In addition, intermediate compositions can be extracted for further work as separate files or streams. See Analysis Display (Section 8.4.2) Calculate Thermal Conductivty The thermal conductivity calculation is relatively slow and complex. This checkbox gives the user contrl over whether it is undertaken See Thermal Conductivity Model help for more details. Gas Heating Values The gas gross and net heating values are now calculated as columns within the calculation table. The value given is derived from the composition of the accumulated gas after sending the fluid through the indicated separator train.

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8.4.1 The Calculation Display A typical CCE display is given in figure 8.9 This Dialogue allows the user to initiate calculations and view the results .

Figure 8.9: Constant Composition Calculation Screen

The Calculation Screen is loaded when the Calculate button is pressed on an Automatic or User Selected Input Dialogue. The display is in the form of a table with input values on the left and the required calculation variables calculations listed in columns on the right. If multiple streams have been selected (see Constant Composion Expansion), the user can move betwen the streams by clicking on the tabs at the bottom of the display.(see PVT Project File Structure for more information on streams. Each column has a variable name and unit as a heading. Scroll bars are provided to show more variables and results. Colours have been used with grids to indicate phase: Red - gas only Blue - mixture of oil and gas Black - oil only If the values have been already calculated the display will show the last set of values calculated. The display has several control buttons along the top which have the following functions: Calculate

This option recalculates the table using the latest inputs provided

PVTP User Guide


Plot

This generates a full sized plot of the calculated results. Layout

This options allows the user to select which columns are displayed in the results table. See Calculation Layout Display . Analysis

This option produces a secondary screen giving the compositions calculated at each measurement point. The analysis screen also provides access to the EXTRACT function which allows the user to export a particular line of the calculation to a PVT file. Alternatively, the intermediate composition can be copied to a stream within this project file.With Separator calculations further information Viz. Total GOR ,Gas Gravity and Oil Gravity are also provided through a More option. Cancel


This option closes down both the calculation and the input displays and passes the control back to the main PVT screen. Clipboard

This sends all or part of the results data to the clipboard by calling the Copy to Clipboard Dialog Hydrate Export

If a hydrate formation Pressure calculation is done the analysis button is replaced by an export version. This allows direct output to an ASCII file which can be taken into Prosper. Note on Density The Calculation table provides 2 alternative values for Oil Density i.e. EOS and KATZ. The EOS value derives strictly from the Equation of State value for Compressibility z and PV=zRT while the other stems from the composition being input into a Standing-Katz density correlation. The values in combination can be used as a guide to the appropriateness of the

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values used to generate the EOS model e.g. BI coefficients, acentric factors , pseudo characterisation etc. The EOS density is used in all subsequent calculations for FVF ,GOR etc. More values can be viewed by using the horizontal and vertical scroll bars provided. 8.4.2 The Analysis Display The screen shows the compositions and calculated K values for each temperature and pressure combination. The other information presented depends on the caculation.The example below is for CCE

Figure 8.10: Constant Composition Expansion Analysis Display

The temperature value displayed can be changed by clicking on the down or up arrow within the temperature area ( top left). The pressure value displayed can be changed by clicking on the down or up arrow within the pressure area ( top right). The command buttons perform the following functions: Exit Close down the display and return to the calculation screen. Clipboard This sends all or part of the analysis data to the clipboard by calling the Copy to Clipboard Dialog Extract

PVTP User Guide


This option allows the user to save the composition( total,vapour or liquid)being stored as a separate PVT file for later retrieval. Alternatively, a stream can be created within the current PVT Project File. The analysis display for a separator calculation is more complex. QUALITY PLOT

Clicking on the Quality Button will automatically generate a quality plot of the type shown below. Background to this plot is descibed in the utility menu help for the Hoffmann Quality Plot. If the properties of the components give a consistent flash, the light components should roughly fall along a straight line.

Figure 8.10b: Analysis Quality Plot

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8.4.3 The Copy to Clipboard Dialog There are two forms:. Calculation Results This dialog is called by clicking on the Clipboard button within the Calculation Results Dialog.

Among the option available are to include the results column names and/or units. In addition the order of the results within the table can be reversed. To send the data to the clipboard, click on OK. Calculation Analysis This dialog is called by clicking on the Clipboard button within the Calculation Analysis Dialog.

Among the option available are to include the analysis column names .All the analysis created within the calculation on the target stream can be sent to the clipboard by clicking on option 2.The last option indicates whether data other than the compositions should be sent.

PVTP User Guide


8.5 Constant Volume Depletion(CVD)

A CVD calculation can be initiated by selecting the Constant Volume Depletion option from the calculation menu or clicking on the icon shown above.

Constant Volume Depletion is a flash process where the volume of the system at Dew Point is preserved. At each flash stage volume in excess of this is removed as excess gas. The excess gas products, i.e. equal to the increase in volume over the initial value, are removed at each stage to become the wellstream production. The liquid and gas equal to the initial volume goes on to be flashed at the next set of conditions. The CVD calculation concentrates on the gas and liquid left in the reservoir, while the Depletion Study (Section 8.6) is used to find the produced gas (Wellstream) data. For example, the GOR displayed for the CVD is that of the oil within the reservoir. The CVD screen has only a manual mode. The CVD screen has an Automatic and Manual Method. The normal mode is User Selected as PVT reports only have a small number of steps. The Automatic mode allows the user to introduce a larger number of small steps. This better represents the calculation path of a program like MBAL. A typical manual mode display being shown in figure 8.12. Entries are provided for the temperature at which the process is to be carried out and the pressure stages involved in the operation. A Clear button removes all entries. The Copy from DEPL button copies across the entries which have been made for the Depletion Study calculation. Separator Data The CVD input displays contain a section for Separator Data. This allows the user to define a separator train through which the CCE liquid will be flashed to correct the Oil FVF and GOR. The processes which are used to return an oil to standard conditions can significantly change the final oil characteristics and the amount of gas liberated on the way. When multiple samples are being analysed, it may be necessary to have individual separator settings for each stream. In this case, the individual radio button should be clicked on. The stream separator settings can be accessed via the tabs at the bottom of the table.All stages do not need to be entered and a last flash to standard conditions is always included.The checkbox within the separator data area switches the correction on and off. The values within this separator data area are loaded and stored separately from those within the Separator calculation. The Copy Sep button will copy the stages from the Separator Calculation into the Separator Data area.The Clear button removes all values from within the Separator Data area.

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Stream Selection

The list box allows the user to select any combination of streams to calculate.See PVT Project File Structure for more information on streams. Volume Shift A volume shift control panel is proved to allow the user to setup and to switch on and off this feature prior to calculation . See Volume Shift and Volume Shift Setup help for more details. Gas Heating Values The gas gross and net heating values are now calculated as columns within the calculation table. The value given is derived from the composition of the accumulated gas after sending the fluid through the indicated separator train. Viscosity Method Various viscosity models have been introduced into the PVTp program (see Section 4.6). Only one model is active in a file at any one time. The active model is selected via the combo box which appears on all the calculation input and regression selection displays.

Note on Oil Density The calculation screen shows two Oil Densities for comparison purposes. The EOS value is determined directly from the equation of state calculation of liquid compressibility Z. This value is used to derive all the related properties i.e. Oil Gravity,Oil FVF and GOR. The second value is taken from the correlation put forward by Standing and Katz. The non-predictive nature of the Equation of State method and its weakness in calculating liquid properties makes the value of Oil Density particularily suspect in non-matched systems. The EOS Density is ,however, sensitive to composition and property changes, making it a suitable value for matching and regression. The Standing-Katz value is empirically derived and in our experience predicts well the density of most fluids. The average nature of the number and its lack of sensitivity make it unsuitable for regression. Matching the EOS density to good experimental data usually results in the two densities having very similar values. Conversely, if the values are very disimilar, it usually means that good matching has not been achieved. Copying And Pasting In common with all the grids within the PVTp program the main grid within this display can be copied onto the clipboard by selecting all the cells and typing Control+C. Pasting from the clipboard is done by clicking within the target cell and typing Control+V.

PVTP User Guide


Figure 8.11: CVD Input Screen

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Stream Selection

The list box allows the user to select any combination of streams to calculate.See PVT Project File Structure for more information on streams. Viscosity Method Various viscosity models have been introduced into the PVTp program (see Section 4.6). Only one model is active in a file at any one time. The active model is selected via the combo box which appears on all the calculation input and regression selection displays.

Volume Shift A volume shift control panel is proved to allow the user to setup and to switch on and off this feature prior to calculation . See Volume Shift and Volume Shift Setup help for more details. Note on Oil Density The calculation screen shows two Oil Densities for comparison purposes. The EOS value is determined directly from the equation of state calculation of liquid compressibility Z. This value is used to derive all the related properties i.e. Oil Gravity,Oil FVF and GOR. The second value is taken from the correlation put forward by Standing and Katz. The non-predictive nature of the Equation of State method and its weakness in calculating liquid properties makes the value of Oil Density particularily suspect in non-matched systems. The EOS Density is ,however, sensitive to composition and property changes, making it a suitable value for matching and regression. The Standing-Katz value is empirically derived and in our experience predicts well the density of most fluids. The average nature of the number and its lack of sensitivity make it unsuitable for regression. Matching the EOS density to good experimental data usually results in the two densities having very similar values. Conversely, if the values are very disimilar, it usually means that good matching has not been achieved. Copying And Pasting In common with all the grids within the PVTp program the main grid within this display can be copied onto the clipboard by selecting all the cells and typing Control+C. Pasting from the clipboard is done by clicking within the target cell and typing Control+V.

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Figure 8.11a: DEPL Input Screen

PVTP User Guide


8.7 Differential Expansion(DIFF)

A DIFF calculation can be initiated by selecting the Differential Expansion option from the calculation menu or clicking on the icon shown above. Differential Expansion or Liberation is a flash process where all the gas products are removed at each stage. The liquid goes on to be flashed at the next set of conditions. The Differential Liberation screen has only a Manual Method , a typical display being shown in figure 8.12. Entries are provided for the temperature at which the process is to be carried out and the pressure stages involved in the operation. A Clear button removes all entries. Points to Remember about a DIFF calculation: ◊ The liquid in the initial stage of a differential liberation , by definition, MUST be at Bubble

Point. Any gas detected by the calculation is ignored and does not appear in any calculated value.

◊ The calculation is very sensitive to the number of steps and the value of each step. Taking a different route to the end point gives very different results

◊ The calculation of GOR is carried out with respect to the Residual Volume of the oil making it very sensitive to each step and particularily to the last. A last step to atmospheric is normal. Unlike the other calculation all stages must be complete before the values at each stage can be properly calculated.

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Figure 8.12: Differential Liberation Input Screen

Viscosity Method Various viscosity models have been introduced into the PVTp program (see Section 4.6). Only one model is active in a file at any one time. The active model is selected via the combo box which appears on all the calculation input and regression selection displays.

Note on Oil Density The calculation screen shows two Oil Densities for comparison purposes. The EOS value is determined directly from the equation of state calculation of liquid compressibility Z. This value is used to derive all the related properties i.e. Oil Gravity,Oil FVF and GOR. The second value is taken from the correlation put forward by Standing and Katz. The non-predictive nature of the Equation of State method and its weakness in calculating liquid properties makes the value of Oil Density particularily suspect in non-matched systems. The EOS Density is ,however, sensitive to composition and property changes, making it a suitable value for matching and regression. The Standing-Katz value is empirically derived and in our experience predicts well the density of most fluids. The average nature of the number and its lack of sensitivity make it unsuitable for regression.

PVTP User Guide


Matching the EOS density to good experimental data usually results in the two densities having very similar values. Conversely, if the values are very disimilar, it usually means that good matching has not been achieved. Stream Selection

The list box allows the user to select any combination of streams to calculate.See PVT Project File Structure for more information on streams. Volume Shift A volume shift control panel is proved to allow the user to setup and to switch on and off this feature prior to calculation . See Volume Shift and Volume Shift Setup help for more details. Copying And Pasting In common with all the grids within the PVTp program the main grid within this display can be copied onto the clipboard by selecting all the cells and typing Control+C. Pasting from the clipboard is done by clicking within the target cell and typing Control+V.

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8.8 Composite Differential Expansion(COMPOS)

A COMPOS calculation can be initiated by selecting the Composite Differential Expansion option from the calculation menu As suggested by the name this option is very like the standard Differential Expansion or Liberation . COMPOS is a flash process where all the gas products are removed at each stage. The liquid goes on to be flashed at the next set of conditions. Unlike the standard DIFF, the GOR and FVF of the excess vapour estimated for the composite option is not calculated with respect to the residual volume. Instead the values are arrived at in a similar way to a CCE or CVD calculation i.e. by doing a series of separator flashes back to stock tank conditions. If no separator stages are entered a single flash is carried out. This removes the heavy dependence on the number of steps and the accuracy of estimating the residual oil which characterises Differential Liberation. It also is closer to what happens in a reservoir. The Composite Differential Liberation calcualtion is similar to the standard version , a typical input dialog is shown in figure 8.12a

PVTP User Guide


Figure 8.12a: Composite Differential Liberation Input Screen

The difference lies in the standard separator input section at the bottom of the dialog. The Copy from DIFF button will copy across entries from the standard Differential Liberation calculation.

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8.9 Separator Process

A Separator calculation can be initiated by selecting the Separator option from the calculation menu or clicking on the icon shown above. The Separator Process flashes the mixture at a fixed set of conditions. The liquid and gas are split off to go on to the next stage of the process. The Separator option has only one input mode. A Separator Input screen has Data entry boxes which are provided for up to 20 separator stages. Enter the pressure and temperature of each stage and click on the Calculate control button. Two modes are available VIZ. Global or Individual. In Global mode all streams will be calculated with the same separator conditions.

Figure 8.13: Separator Process Input Screen

PVTP User Guide


In Individual mode all streams will be subjected to their own separator conditions. The tabs at the bottom of the grid can be used to move between the stream inputs. The Copy Settings to All Streams will set all stream settings to the current stream value.

Figure 8.13b: Separator Process Input Screen

The separator calculation screen is the same as that described for Constant Composition Expansion (section 8.4) The analysis screen is also much the same as that described in section 8.4.2. The difference is that the More control button now becomes active . Clicking on this brings up a display of the type shown in figure 8.12. giving GOR ,Oil gravity and Gas Gravity values for the selected. Stream Selection

The list box allows the user to select any combination of streams to calculate.See PVT Project File Structure for more information on streams. Volume Shift A volume shift control panel is proved to allow the user to setup and to switch on and off this feature prior to calculation . See Volume Shift and Volume Shift Setup help for more details.

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Note on Oil Density The calculation screen shows two Oil Densities for comparison purposes. The EOS value is determined directly from the equation of state calculation of liquid compressibility Z. This value is used to derive all the related properties i.e. Oil Gravity,Oil FVF and GOR. The second value is taken from the


Figure 8.14: Separator Process Analysis Screen

Figure 8.14a: Separator Process Analysis Summary Table

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QUALITY PLOT

Clicking on the Quality Button will automatically generate a quality plot of the type shown below. Background to this plot is descibed in the utility menu help for the Hoffmann Quality Plot. If the properties of the components give a consistent flash, the light components should roughly fall along a straight line.

Figure 8.14b: Separator Process Analysis Quality Plot

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8.10 Compositional Gradient

A Compositional Gradient calculation can be initiated by selecting the Compositional Gradient option from the calculation menu or clicking on the icon shown above. Compositional Gradient calculates the changes in composition with depth above and below the reference depth. The calculation input screen comes in two forms viz. Automatic (figure 8.15) and User Selected Entry (figure 8.16). Automatic A typical input screen is given in figure 8.15 The display contains radio buttons which allow the user to swap between User Selected and automatic modes. The reservoir reference conditions are also displayed . These variables cannot be changed from this display . Use the Data | Reference Data option (section 7.7) if a change is required. In addition, data boxes are provided for entering the limits of the depth to be covered above and below the reference depth and the number of points to be calculated for each direction. The points will be spread evenly throughout the ranges selected. A check box is provided for swapping between relative and absolute depths. Temperature Gradient must also be entered in the appropriate box. To initiate the calculation click on the Calculate control button. The Calculation Screen and its options are described in section 8.9.1 Saturation Pressure As part of the gradient calculation, the saturation pressure of the mixture can be calculated at each depth. Since this calculation takes some time the option is given to leave out the calculation. Both User Selected and Automatic dialogues contain a check box for this option. If the Saturation Pressure is calculated a plot with Pressure Gradient against depth becomes available . A typical plot is shown in figure 8.15a.

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Figure 8.15: Auto Mode Gravitational Gradient

NOTE the additional information on the plot i.e. Reference Depth,Reference Pressure etc. using the Match point colour (see Plotting) Stream Selection

The small table allows the user to select any combination of streams to calculate.Selected stream are highlighted in red. See PVT Project File Structure for more information on streams. The reservoir reference conditions are also displayed within this table . These variables can be changed from this display . Alternatively, the Data | Reference Data option can be used to view or change thes values. An input screen contains radio buttons which allow the user to swap between User Selected and Automatic modes.

PVTP User Guide


Separator Data The COMPGRAD input displays contain a section for Separator Data. This allows the user to define a separator train through which the CCE liquid will be flashed to correct the Oil FVF and GOR. The processes which are used to return an oil to standard conditions can significantly change the final oil characteristics and the amount of gas liberated on the way. When multiple samples are being analysed, it may be necessary to have individual separator settings for each stream. In this case, the individual radio button should be clicked on. The stream separator settings can be accessed via the tabs at the bottom of the table.All stages do not need to be entered and a last flash to standard conditions is always included.The checkbox within the separator data area switches the correction on and off. The values within this separator data area are loaded and stored separately from those within the Separator calculation. The Copy Sep button will copy the stages from the Separator Calculation into the Separator Data area.The Clear button removes all values from within the Separator Data area.


Volume Shift A volume shift control panel is proved to allow the user to setup and to switch on and off this feature prior to calculation . See Volume Shift and Volume Shift Setup help for more details.

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User Selected A typical input screen is given in figure 8.16 The display contains radio buttons which allow the user to swap between User Selected and automatic modes. In addition, 10 data boxes are provided for entering the depths above and below reference depth at which the gradient is to be calculated. The points do not need to be evenly spread. As in the Automatic mode, an entry is also required for temperature gradient and a check box is provided for swapping between relative and absolute depths. To initiate the calculation click on the Calculate control button. The Calculation Screen and its options are described in section 8.9.1.

Figure 8.16: Compositional Gradient Manual Mode

To initiate the calculation click on the Calculate control button. The Calculation Screen and its options are described in section 8.8.1

PVTP User Guide


8.10.1 Calculation Results Display A typical results display is shown in figure 8.17. The results are reported against the gradient points entered. The controls on this display have the same effect as those described for Constant Composition Expansion (section 8.4). Note on Oil Density The calculation screen shows two Oil Densities for comparison purposes. The EOS value is determined directly from the equation of state calculation of liquid compressibility Z. This value is used to derive all the related properties i.e. Oil Gravity,Oil FVF and GOR. The second value is taken from the correlation put forward by Standing and Katz. The non-predictive nature of the Equation of State method and its weakness in calculating liquid properties makes the value of Oil Density particularily suspect in non-matched systems. The EOS Density is ,however, sensitive to composition and property changes, making it a suitable value for matching and regression. The Standing-Katz value is empirically derived and in our experience predicts well the density of most fluids. The average nature of the number and its lack of sensitivity make it unsuitable for regression. Matching the EOS density to good experimental data usually results in the two densities having very similar values. Conversely, if the values are very disimilar, it usually means that good matching has not been achieved.

Figure 8.17: Compositional Gradient Calculation Results Display

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8.11 Swelling Test

A Swelling Test calculation can be initiated by selecting the Swelling Test option from the calculation menu or clicking on the icon shown above.

This option only becomes available if a second stream or more streams have been defined. The Swelling Test mixes a pre-entered amount of the second stream with the first. The Saturation Pressure of this new mixture is determined. The mixture is the flashed at the Saturation Pressure to get the phase properties. The Swelling Test option has only one input mode. A typical input display is shown in figure 8.18 A Swelling Test Input screen has Data entry boxes which are provided for up to 10 temperatures. In addition 10 second stream compositions can be entered for each temperature . When mixed these numbers represent the mole percent of the second stream within the first. If the component exists within the first stream the values are added together and the properties of the primary stream (eg from regression) are used for both. If no component exists of the same type a new component is created with the properties shown for the second stream. The Swelling Test has two input options for composition VIZ

◊ Mole % ◊ Volume of gas per volume of oil

The input type is set by two radio buttons which are situated beneath the input columns. When either option is selected, the other is automatically calculated aand appears on the calculation display. The unit for vol/vol input can be changed on the units display by scrolling down to the Swelling Input unit. At present the units are set as volumes of gas at standard conditions being added to oil at its saturation pressure. The first step in the calculation is therefore to find the saturation pressure of the oil and the density at that pressure. This density allows the vol/vol input to be translated to its equivalent mole % value. The calculation then proceeds as normal using this value. The Auto Set button sets the compostions to a range between 0 and 90%. The Clear button removes all composioion entries. Enter the temperatures and compositions required and click on the Calculate control button. Analysis For each calculation carried out, the analysis display presents information on compositions K values,gas and oil gravities etc. In addition, intermediate compositions can be extracted for further work as separate files or streams . See Analysis Display for CCE

PVTP User Guide


Figure 8.18: Swelling Test Input Screen

Note : The Swelling Test Saturation Pressure is available for matching .

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8.12 Slim-tube Simulation

A slim-tube calculation can be initiated by selecting the Slim-tube simulation option from the calculation menu or clicking on the icon shown above. This cell to cell model simulates gas injection into an oil reservoir. The program sets up a series of cells as shown in figure 1below. The cells do not need to be the same size but usually are. The temperature of all the cells remain the same at the initial reservoir value. If the cell orientation is horizontal all the cells start at the designated reservoir pressure.If the cells are inclined or vertical, the pressures are adjusted for the column of oil above the cell.

Excess Ga

Cell 1

s & Oil Excess Gas & Oil

Cell 2 Cell n

Injection gas Wellstream

Fig 1 Slim-tube Simulator

In each time step gas is added to the system. The gas injected into cell 1 is mixed with the fluid there and the combination is flashed to find the new amount of gas and oil and their properties. Material Balance calculations and phase mobility criteria are used to calculate how much of each phase is moved to cell 2. Again the new mixture is flashed and the excess is moved to cell 3. This process is repeated until the production cell is encountered. At this point the excess volume and composition appear as wellstream products. Whether multiple contact miscibility is achieved is usually taken from the estimation of the minimum miscibility pressure (MMP). Definitions of the MMP can vary, but it is usually taken as the pressure at which the recovery is 90% wnen 1.2 pore volumes of gas have been injected. At pressures above MMP the gas is assumed to be miscible.

PVTP User Guide


8.12.1 Slim-tube Input dialog This Dialog is the main one for the slim tube simulation calculation. The reasoing behind the calculation is described in Background to Slim-tube Simulation. The screen is brought up by selecting the Slim-tube Simulator option from the main Calculation menu. The dialog gives access to the other slim tube setup dialogs i.e. Cells Setup Rel Perms Setup Times and Material Balance Setup. Set All Values to Default The slim-tube calculation is complex to set up. As it is trying to simulate a physical test , many variables (physical sizesates permeabilities) have to be tuned to realistic values. To help in this process a set of typical default values are provided. Clicking on this button will fill all the Slim-tube dialogs with numbers which will work for most oil/gas combinations. WARNING: Using this button will overwrite all previously entered data (except pressures) on all Slim-tube dialogs. The dialog has 2 modes Automatic and User Selected . Radio buttons are provided to switch between modes. A typical Automatic mode display is shown in figure 8.19:

Figure 8.19: Slim-tube Input Dialog

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A pressure range is entered as a minimum and maximum pressure plus a number of steps. It should be noted that the slim tube simulation is a complex calculation and can be slow. If discrete pressure values are required the mode should be changed to User Selected and the pressures entered as shown in figure 8.21:

Figure 8.21: Slim-tube Input Dialog

Stream Data The reservoir stream is the oil which will fill the slim-tube cells. The injected stream is the gas which will be introduced to test its miscibility in the oil. Temperature The slim-tube experiment is normally done at reservoir temperature. This value will default to the entered reservoir temperature (see Reference Data) , but it can be changed to a different value using the edit box provided. Test for MMP The minimum miscibilty pressure (MMP) is normally taken as the pressure at which there is 90 percent oil recovery at 1.2 pore volumes of gas injected. Above this pressure the gas is taken as being miscible. The test values can be changed from the defaults using the edit boxes provided. The selected values appear as reference lines on the plot of recovery versus pore volume injected. A typical plot is shown below:

PVTP User Guide


Figure 8.22: Slim-tube Output Plot

Setup Cells

The number and dimensions of the cells within the slim-tube are setup in the Cells Setup Dialog. Setup Relative Permeabilities

The relative permeabilities and associated data are entered within the Rel Perms Setup Dialog. Setup Times and Material Balance limits

The number and size of the time steps are setup within the Times and Material Balance Setup Dialog.

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Clear

Clear will remove the current pressure inputs. Calc

When all entries have been made click on Calc to bring up the Slim-tube Calculation Dialog. Volume Shift A volume shift control panel is proved to allow the user to setup and to switch on and off this feature prior to calculation . See Volume Shift and Volume Shift Setup help for more details.

PVTP User Guide


8.12.2 Slim-tube cell data dialog This Dialog sets up the dimensions and other data related to the cells that make up the slim-tube. The display is called by the Slim-tube Input Dialog. A typical screen would be as in figure 8.23:

Figure 8.23: Slim-tube Cell Data Dialog

The first step is to define the number of cells. The Production cell is normally the last and the injection is the first. The depth is only for reference. The cells are normally horizontal. in this case they are all at the same depth and pressure. If they are vertical , they are at different pressures depending on the cell height and the oil density. The cells can contain the same data. to do this enter the data into cell 1 and click on the Copy Cell 1 Data to All button. Alternatively, all data can be individually entered within the table. The first three columns define the dimensions of each cell . The last two indicate the Porosity and Permeability of each cell.

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8.12.3 Slim-tube cell data dialog This Dialog sets up the relative permeability and capillary pressure data which governs the relative movement of fluids in the slim-tube. In addition , the rock compressibility can be entered within this dialog. The display is called by the Slim-tube Input Dialog. A typical screen would be as in figure 8.24:

Figure 8.24: Slim-Permeabilities Dialog

The Relative Permeability data can only be entered in table form at present. The exponents are entered as fractions with respect to the oil saturation. A Capillary Pressure curve can also be entered as a function of oil saturation.

PVTP User Guide


8.12.4 Slim-tube time steps dialog This Dialog sets up the time steps and material balance options within the slim tube simulator. The display is called by the Slim -tube Input Dialog. A typical screen would be as in figure 8.25:

Figure 8.25: Slim-tube time steps Dialog

Enter the number of time steps required. This action will set the size of the table. The times can be set as a fixed value or with a different value for each step. To set the same time for each step click on the fixed time step radio button and enter the time required in the edit box provided. If different times are required,click on the variable time step radio button and enter the times within the table. Adaptive Time Steps It should be noted that the program will automatically change the value of a timestep or add more timesteps if it is failing to meet its convergence criteria.

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8.12.5 Slim-tube calculations dialog This Dialog allows the user to initiate calculations and view the results .

Figure 8.26: Slim-tube Calculation Dialog

The Calculation Screen is loaded when the Calculate button is pressed on the Slim-tube Input Dialog. The display is in the form of a table with a Cell Detail button as the first column. The properties listed are those of the fluid exiting the last cell at the end of the time step. The time steps listed may chage from those entered initially as the calculation will create new values to reflect the intermediate flow changes within the model. Cell Detail Clicking on any of these buttons will bring up the Cell Detail Dialog . This displays the phase ,properties and compositions in each cell at the selected timestep.Any composition can be extracted as a strem for further analysis.(see PVT Project File Structure for more information on streams) If multiple pressures have been selected (see Slim-tube Input Dialog) the pressures appear as separate tables with tags at the bottom. The user can move betwen the pressures by clicking on the tabs at the bottom of the display. Each column has a variable name and unit as a heading. ScroCellc3-9ition can be


If the values have been already calculated the display will show the last set of values calculated. The display has several control buttons along the top which have the following functions: Calculate

This option recalculates the table using the latest inputs provided Plot

This generates a full sized plot of the calculated results. Analysis

This option produces a secondary screen giving the compositions calculated at each measurement point along with details of the material balance found at the end of the time step. The analysis screen also provides access to the EXTRACT function which allows the user to export a particular line of the calculation to a PVT file. Alternatively, the intermediate composition can be copied to a stream within this project file. Cancel


This option closes down both the calculation and the input displays and passes the control back to the main PVT screen. Clipboard

This option allows the user to send the table results with/or without headings to the clipboard.

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8.12.6 Slim-tube analysis dialog This Dialog is called by clicking on the Analysis button within the slim-tube calculation display. The compositions shown are those of the fluids being produced from the designated production cell. The numbers within the table give an indication of the material balance of each component after the timestep. The composition within each cell can be viewed using the Slim-tube Cell Detail Dialog.

Figure 8.27: Slim-tube Analysis Dialog

The pressure run being viewed can be changed using the combo box provided. The time step value displayed can be changed by clicking on the down or up arrow on the units or tens control. Units will add or subtract 1 to the time step. Tens will add or subtract 10 to the time step. The command buttons perform the following functions: Exit Close down the display and return to the slim-tube calculation display. Extract This option allows the user to save the composition( total,vapour or liquid)being stored as a separate PVT file for later retrieval. Alternatively, a stream can be created within the current PVT Project File.

PVTP User Guide


8.12.7 Slim-tube cell detail dialog This gives more detail on the contents of each cell during a time step. The display is called by clicking on the CELL DETAILS button within the slim-tube calculation dialog.

Figure 8.28: Slim-tube Cell Detail Dialog

For each cell the table gives details of the phase,cell pressure,IFT,oil saturation and oil and gas viscosities. In addition the composition within the cell is given. If the calculation goes into adaptive mode, the result number will not be equivalent to the time step. The cell compositions can be extracted to another stream for further analysis by: 1. Entering the required cell number in the edit box, or clicking on the arrow buttons until the required value is reached. 2. Clicking on the Cell Composition to Stream Button.

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PVTP User Guide

8.13 Quick Calculation Control Button A subset of the Equation of Sate Calculations is available by clicking on the Quick Calc. control button within the Recombination, Edit Composition and View Properties displays (see Chapter 7)

Figure 8.309: Calculate Button Options

This feature provides the user with access to a subset of the calculation menu as a means of checking the consistency of the entered composition information. The small display (figure 8.30) provides options to calculate :

◊ Phase Envelope ◊ Critical Point (Temperature and Pressure) ◊ Saturation Pressure (at the reference temperature) ◊ Flash to Standard Conditions ◊ Flash Through Separator Stages ◊ Calculate Maximum Water in the Hydrocarbon Phase

The Phase Envelope and Critical Point calculations are identical to those described in sections 8.1 and 8.2 .The Saturation Pressure option does not use the same method as the ranged equivalent (section 8.3) . The calculation is done at reference conditions only giving an output of the type shown in figure 8.31


PVTP User Guide

8.13.1 Small Separator Calculation Dialog This display is called from the Quick Calculation Dialog.

Figure 8.33: Small Separator Calculation Dialog

The objective is to provide a separator calculation which quickly provides the basic data of Oil density and Gravity, Gas Gravity and GOR. If separator conditions have already been defined the values will appear. If not enter the temperatures and pressures in the Edit Boxes provided in the Values section of the display. When ready click on Calc Clear removes all entries and results.

9 Calculation of Solids This section describes the calculations available for solids. The alternatives are: Waxes Wax Amount - Enter a range of temperatures and pressures and perform a multiphase flash to

find the amount in the solid phase. Wax Appearance Temperature – Select a pressure and find the temperature at which wax just

starts to form. Hydrates Hydrate Formation Pressure - Enter a range of temperatures and find the minimum pressure at

which hydrates will form. Minimum Inhibition Concentration – Select a temperature and pressure and find the

concentration of inhibitor at which hydrate just starts to form under these conditions. Details of Wax and Hydrate modelling and the model alternatives and references are given in Chapter 4. 9.1 Wax Amount Calculation This calculation can be initiated by selecting the Wax Amount (Multiphase Flash) from the Calc Solids menu:

Two modes are available for data input VIZ. Automatic and User Selected. The mode can be changed using the radio buttons at the top right of the display. This dialogue is used for Automatic Input for the Wax Amount calculation (figure 9.1). Data entry boxes are provided for entering the limits of the temperature and pressure ranges to be covered and the number of points to be calculated for each variable. The points will be spread evenly throughout the temperature and pressure ranges selected. Note that the wax formation effect is very much driven by temperature and very little pressure dependence is shown


Figure 9.1: Wax Amount Automatic

In the User Selected version the ranged input is replaced by a grid where any mixture of pressures and temperatures can be entered Figure 9.2: Wax Amount User Selected

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Chapter 9 - Calculation of Solids 3 - 14

Stream Selection

The list box allows the user to select any combination of streams and archives to calculate.See PVT Project File Structure for more information on streams. Model Selection

A combo box allows the user to select between the various wax models.Clicking on the Reset Props button resets the important component properties back to the default values outlined by the model's author. WARNING using this button will reset any solids regression that has been done. See Wax Modelling ,Chapter 4, for more details on the model types available. See Lab Data/Matching ,Chapter 7, for more details on what can be matched for solids. Pressure Range The lower pressure limit of the calculation has been set at 0 psig (14.7 psia). If a value below this limit is entered The following message will appear

At least one pressure and temperature should be defined before proceeding to the Calculation Dialogue.

To bring up the calculation dialogue click on the Calc control button. The calculation dialog which appears is similar in structure and features to that described for the two-phase flash CCE calculation (Section 8.4.1)


Clear removes any entered values

PVTP User Guide


9.1.1 The Analysis Display This display is called by clicking on the analysis button within the calculation table display (Section 8.4.1). The screen shows the compositions for each phase at each combination of temperature and pressure . Figure 9.3: Wax Amount Analysis Display.

The temperature value displayed can be changed by clicking on the down or up arrow within the temperature area ( top left). The pressure value displayed can be changed by clicking on the down or up arrow within the pressure area ( top right). The command buttons perform the following functions: Exit Close down the display and return to the calculation screen. Extract This option allows the user to save the composition( total,vapour or liquid)being stored as a separate PVT file for later retrieval. Alternatively, a stream or archive can be created within the current PVT Project File.

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9.2 Wax Appearance Temperature This calculation can be initiated by selecting the Wax Appearance Temperature from the Calc Solids menu:

Two modes are available for data input VIZ. Automatic and User Selected. The mode can be changed using the radio buttons at the top right of the display. This dialogue is used for Automatic Input for the Wax Amount calculation. Figure 9.4: WAT Automatic

In addition, data entry boxes are provided for entering the limits of the temperature and pressure ranges to be covered and the number of points to be calculated for each variable. The points will be spread evenly throughout the pressure ranges selected. Note that the wax formation effect is very much driven by temperature and very little pressure dependence is shown In the User Selected version the ranged input is replaced by a grid where any mixture of pressures can be entered

PVTP User Guide


Figure 9.5: WAT User Selected

Stream Selection

The list box allows the user to select any combination of streams and archives to calculate.See PVT Project File Structure for more information on streams. Model Selection

A listbox allows the user to select any or all of the available wax models.As the calculation progresses the wax dependent properties of the component(s) are reset to those values suggested in the model. If however regression is used to set a property eg. the Melting point of the heaviest component,this will not be reset during the WAT calculation. See Wax Modelling ,Chapter 4, for more details on the model types available. See Lab Data/Matching ,Chapter 7, for more details on what can be matched for solids.

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Pressure Range The lower pressure limit of the calculation has been set at 0 psig (14.7 psia). If a value below this limit is entered The following message will appear

At least one pressure should be defined before proceeding to the Calculation Dialogue.



Clear removes any entered values Calculation Limits

Some of the limits of the calculation can be adjusted in this section of the dialog. The minimum and maximum temperatures dictate the range in which wax will be looked for. The maximum number of steps sets how many iterrations the program allows before it gives up looking for a solution.The minimum test solid percent is the value used to determine if wax is just forming i.e. the WAT. The program looks for a value of percent solids between zero and the Min Test Solid % to say that it is at the Wax Appearance Temperature.

PVTP User Guide


9.3 Hydrate Formation Pressure This calculation can be initiated by selecting the Hydrate Formation Pressure Option from the Calc Solids menu:

Hyrates are important to the petroleum industry because they form at tempertures above that of normal ice. Plugging due to hydrate formation can potentially occur at any location from the resevoir to surface where the pressure is greater than the minimum value for the fluid temperature. For a range of Temperatures the program will calculate the minimum pressure at which hydrates will form. More details on the formation of these troublesome clathrates is given in Background to Hydrates ,Chapter 4. This dialogue is used for Automatic Input for the Hydrate Formation Pressure calculation. Figure 9.6: Hydrate Formation Pressure Automatic

All boxes should have an entry before proceeding to the Calculation Dialogue. Stream Selection

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The list box allows the user to select any combination of streams and archives to calculate.See PVT Project File Structure for more information on streams. This display contains radio buttons which allow the user to swap between User Selected and Automatic modes. In addition, data entry boxes are provided for entering the limits of the temperature range to be covered and the number of points to be calculated. The points will be spread evenly throughout the temperature and pressure ranges selected. Model Options

This area allows the user to select from different models which vary in the main in the estimation of the Langmuir Adsorption Constant. See Hydrate Modelling for more details. In addition a checkbox allows the user to select whether Hydrate II should be calculated. Since petroleum fluids normally contain significant amounts of C1 and C2 , Hydrate I will normally form first. See Background to Hydrates, Chapter 4, for information. Inhibitor Data Figure 9.7: Inhibitor Entry

This area allows the user to calculate the effect of adding various inhibitors to the fluid. A combo box allows the user to select from a list of common inhibitors. Up to 5 inhibitor concentrations can be entered using the edit box provided.All values should be in weight percent. The Clear Percents button removes all entries while the check box allows the user to switch on and off the calculation without loosing the entries. More information on inhibitors is given in Hydrate Inhibition. See also help on the Minimum Inhibitor Concentration calculation Restrictions 1) At present, the calculation has been limited to that where the hydrate is in equilibrium with liquid water i.e. to temperatures above 0.1 degrees C and 32.2 degrees F. If too low a pressure is entered the following message is displayed

PVTP User Guide


2) No hydrate calculation can be carried out with a Grouped composition. The modelling of hydrates is dependent on the identification of the type and amount of the individual small gas molecules which become entrapped in the ice. Only ungrouped compositions allow these species to be identified. See Background to Hydrates. for more details. Attempting to enter a hydrate calculation with a grouped composition will produce the following message:

Control Buttons



Clear removes any entered values In the User Selected version the ranged input is replaced by a grid where any mixture of temperatures can be entered:

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Figure 9.8: Hydrate Formation Pressure User Selected

PVTP User Guide


9.3.1 Calculations Dialog The Calculation dialog is very similar to that described for CCE in section 8.4. The difference occurs when any inhibitor concentrations are requested. A typical display is shown in figure 9.9 Figure 9.9: Hydrate Formation Pressure Results

The selected inhibitor concentrations are coloured red and the new pressure values are shown immediately afterwards. When complete the results are available for export to Prosper by clicking on the Export button (see Section 3.1.5) 9.4 Hydrate Minimum Inhibitor Concentration This calculation can be initiated by selecting the Hydrate Min. Inhibitor Concentration from the Calc Solids menu:

Hyrates are important to the petroleum industry because they form at tempertures above that of normal ice. Plugging due to hydrate formation can potentially occur at any location from the resevoir to surface where the pressure is greater than the minimum value for the fluid temperature. Inhibitors raise the pressure at which a hydrate forms for a particular temperature. This calculation estimates the amount of a selected inhibitor required to provide no hydrate formation at an entered temperature and pressure.

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More details on the formation of these troublesome clathrates is given in Background to Hydrates ,Chapter 4. Figure 9.10: Hydrate Formation Pressure Results

A pressure(P) and temperature(T) must be entered in the edit boxes provided. The program calculates what inhibitor concentration which gives the start of hydrate formation at the entered T and P. Procedure 1) Enter a T and P. 2) Select an inhibitor and a model. 3) Press Calc. and the answer will appear as a weight and mole percentage in the results section

at the bottom of the display. See also Hydrate Modelling and Hydrate Inhibition (Chapter 4). Stream Selection

The combo box allows the user to select the active stream and archives to calculate.See PVT Project File Structure for more information on streams. In addition, data entry boxes are provided for entering the limits of the temperature range to be covered and the number of points to be calculated. The points will be spread evenly throughout the temperature and pressure ranges selected. Model Options

This combo box allows the user to select from different models which vary in the main in the estimation of the Langmuir Adsorption Constant. See Hydrate Modelling for more details. Restrictions

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1) At present, the calculation has been limited to that where the hydrate is in equilibrium with liquid water i.e. to temperatures above 0.1 degrees C and 32.2 degrees F. If too low a temperature is entered the following message is displayed

2) No hydrate calculation can be carried out with a Grouped composition. The modelling of hydrates is dependent on the identification of the type and amount of the individual small gas molecules which become entrapped in the ice. Only ungrouped compositions allow these species to be identified. See Background to Hydrates (Chapter 4). for more details. Attempting to enter a hydrate calculation with a grouped composition will produce the following message:

10 Reporting This section describes the reporting options and procedures used in the PVT package. 10.1 Setting Up the Reporting System Figure 10.1 Report Directories Setup

Under the Report option on the main menu there is a Setup Report Directories option. On selecting this you are presented with a dialogue which requires three pieces of information. The first of these is where the default or system report templates are stored. This is the path to an archive file which contains the system report templates in a compressed form. This file will normally be in the same directory as the PVTP executable. The next field in the dialogue requires the path to the default directory where reports printed to file are to be placed and the final field is the path to a directory where user defined report templates are to be stored. 10.2 Reports The reporting interface gives you complete control over how your reports are formatted and what information is utilised to make up the report. This is facilitated by the use of report templates which can be edited to suit your own requirements. You can choose to use the default report templates provided with the system or can choose to create your own slightly different versions of these reports. The selected templates can then be used to generate the actual reports which can be sent to a variety of places (printer, file or screen). The report templates are displayed in a hierarchy and all templates which have been selected (by double-clicking on it) show an X in the check-box beside the template name. The colour of this X denotes whether it is the system (black) template or a user defined (red) template which is being used. There are two modes for the editing of report templates: System and User. System mode does not allow you to change any template whereas User mode allows you to create new user defined templates from scratch or based on an already existing system report template and also allows you to edit an existing user defined report template. Selecting User mode also makes the User Reports section of the template hierarchy visible. The User Reports hierarchy contains all report templates which have been tagged as being a derivation of a system report template as well as any free standing user defined templates.

2- 12 PVTP User Guide

Figure 10.2 Main Window

The reporting main window consists of four main parts: The command segment at the top of the dialogue containing the buttons, the report selection hierarchy, the output device selection group and the template type selection group. The output device group is only used when printing from selected report templates. The available commands are:

OK Print the selected reports to the selected output device and terminate the dialogue

Cancel

Terminate the dialogue

Help Bring up the on-line help window Setup Select a Printer User Switches between System and User edit mode, this shows or hides the User

Reports section of the report hierarchy and enables or disables the Create and Edit buttons. If in User mode this button shows the text ‘System’ and vice-versa.

View View a previously saved native format file on-screen. This brings up a file selection box for choosing the appropriate report and passes this file name to the Report Executor

Print Print the selected reports to the selected output device Create Create a new user report Edit Edit an existing user report template or create a new template from a system

template Group Allows the grouping of report templates references and the storing of the group

information in a file for later recall. This allows batch printing of reports for any analysis

The available output types are:

Printer Sent the report to the current printer Screen The reports are displayed on-screen in a report executor window Native File The reports are saved as .FR files in the output reports directory RTF File The reports are saved as RTF files in the output reports directory Text File The reports are saved as tab delimited text files for easy spreadsheet import

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Chapter 10 - Reporting 3 - 12

The native (.FR) file format can only be read by the reporting system whereas the RTF format can be read by many Windows word processing applications. When printing to file you will be presented with the following dialogue: Figure 10.3 File naming window

The default directory will be set to the default output directory but this can be altered using the Select Directory button. This can then be applied to all output files by using Change All. If it is necessary to change the output directory of one of the files, this can be achieved by using the Browse button associated with each report. The filenames can themselves be edited in the text box which contains them. For any given report in the system hierarchy you can choose to view or print a report using either the system report template provided or a user defined report template based on that system report template (or at least that position in the hierarchy) or you can choose a report grouping which can be made up from a combination of user and system reports. You choose between these options using the report template type selection group at the bottom right of the main window. If you select the user report template option for any hierarchy position and there are multiple user defined report templates for that position then a dialogue appears which allows you to select the particular template that you want.

Figure 10.4

User-Defined Report Template Selection Dialogue

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Double clicking on any of the report templates (or selecting and pressing Ok) will cause it to become the user defined report template for that hierarchy position for the current reports session. The default choice is the topmost user defined report template. You can stop a user defined report template from being associated with that hierarchy position by selecting it and then pressing Delete. This does not actually delete the report template (it can still be seen within the User Reports section of the hierarchy). If you are selecting a report grouping then a similar dialogue appears and you can select the appropriate group file. After you have selected a file all the reports referenced in the group will appear ‘checked’ in the hierarchy and you can then press print for all of these reports to be sent to the selected output device. 10.3 Template Editor Commands The template editor works on the principle of moveable fields or groups of fields where the inputs to these fields can be any value from PVTP. You can define headers and footers which can be shown on each page, have fields which have a value which is the result of a calculation or even have groups of fields which are displayed only if a condition is met. Figure 10.5 Template Editor Window

Data fields from PVTP are added using the F2 key, selecting the data items required and then pressing Ok when finished. The selected data items will then appear as fields, one by one, as the left mouse button is clicked. You can roughly position the fields in this way. You are not limited to one pass at adding data items to the report template. More items can be added at any time in the same manner. Once a field has been added to the report template you can edit some of the properties of the text which will be shown in the field and assign a group number to the field by double clicking the left mouse button on it and the font properties can be changed by double clicking the right mouse button on it. Other properties, such as whether the field has a box around it, etc., can be changed through the menu options, a full description of which are given below.

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Figure 10.6 Selection of data items

The template editor commands can be selected by using the menu, toolbar or keyboard shortcuts. You can get help on any menu item by highlighting the menu item and then pressing the F1 key or by consulting the index of help topics under the help menu. File Menu This menu contains commands for saving the current report template file and specifying the report template parameters.. Save: Use this selection to save the current report template to the current file name. If a file is not yet specified, the form editor will prompt you for a file name. If you do not provide a file extension, the editor automatically appends a .FP extension to the report file. If a file with the same name already exists on the disk, the form editor will save the previous file with a backup extension (.RE). Save As: This selection is similar to Save File. In addition, it allows you to save the report template to a new file name. Report Parameters: This option allows you to set certain report parameters. Firstly, you can specify the name of the report. You can set the margin for the printed page. You can instruct the report executor to print trial records for adjusting forms such as labels and invoices. You can also specify the default date format for input. The date format that you specify here will be enforced for parameter input during the report execution session, and any date constant used in expressions. Report Filter: This option allows you to enter a filter criteria for the report. Each data record will be tested with the expression that you provide here. A record is selected only if this expression evaluates to a TRUE value. For example, if the expression was sales->amount>100, then only the records with the sales amount more than 100 will be selected.

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Printer Setup: This option allows you to select a printer from a list of installed printers and invoke a printer specific dialogue box for the selected printer. You select the parameters from a set of printer specific options. These options include page size, page orientation, resolution, etc. The printer options that you select here determine the width and height of the report. Exit: Use this function to exit from the form editor session. If the current file is modified, you will have an option to save the modifications. Edit Menu: This menu contains commands to edit the report objects. One or more report objects must be selected before using this option: Cut: Use this option to copy the current item or all the items in the current selection to the clipboard. The copied items are deleted from the form. Copy: Use this option to copy the current item or all the items in the current selection to the clipboard. Paste: Use this option to paste the items from the clipboard to the current form. Position Text: Use this option to position the text within the item boundaries. The text can be justified on the left, right, top, or bottom edges, or it can be centred horizontally or vertically. This option is valid for the label and field type items only. Item Outlines: Use this option to specify the item boundaries (left, right, top, bottom) to draw for one or more selected items. You can also specify the colour and width of the boundary lines.

Item Background: Use this option to set the background colour or pattern for one or more selected items. Centre Horizontally: This option is used to centre horizontally one or more selected items. When more than one item are selected, the form editor first centres the selection rectangle and then moves the selected items such that the position of the selected items relative to the selection rectangle does not change. Delete Item: Use this option to delete one or more currently selected items. If the current section is being deleted, the program asks for your confirmation before the deletion. All items within the section are also deleted. Fonts: Use this function to change the font and colour for the text for one or more selected objects. This option is valid for the field and label type objects only. When you select this option, the form editor shows the font and colour selection dialogue box. The current font and colours are preselected in the dialogue box. Use this dialogue box to specify your selections.

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Snap to Grid: This option allows you to turn on or off the invisible grid on the form. When the grid is turned on and an item is moved, it automatically aligns to the closest grid location. This option also allows you to set the grid width.

Report Size: The following options shrink or elongate the report in the horizontal or vertical direction by the amount equal to the width or the height of the selection rectangle. Expand Horizontally Use this option to create horizontal space by moving items horizontally. For example, consider three items, A, B, and C placed horizontally. If you need to insert a new item between the items A and B, you can use this function to create the desired space between these two items and place the new item in the newly created space. To move the items B and C toward right, create a selection rectangle after the item A and select this option. The width of the selection rectangle specifies the movement of the items B and C toward right (noted that the selection rectangle does not need to include all items to be moved). All items toward the right of the selection rectangle and with the vertical placement between the vertical space spanned by the selection rectangle are moved. Expand Vertically Use this option to create additional vertical space by moving the items downward. For example, consider three items, A, B, and C placed vertically. If you need to insert a new item between items A and B, you can use this function to create the desired space between these two items and place the new item in the newly created space. To move items B and C downward, create a selection rectangle below the item A and select this option. The height of the selection rectangle specifies the downward movement of items B and C (noted that the selection rectangle does not need to include all items to be moved). All items below the selection rectangle are moved. This option also expands (vertically) the current section by the height of the selection rectangle. Compress Horizontally Use this option to delete extra horizontal space by moving items horizontally. For example, consider three items, A, B, and C placed horizontally. You can use this function to bring items B and C closer to the item A. To move items B and C toward left, create a selection rectangle after the item A and select this option. The width of the selection rectangle specifies the movement of items B and C toward left (noted that the selection rectangle does not need to include all items to be moved). All items toward the right of the selection rectangle and with the vertical placement between the vertical space spanned by the selection rectangle are moved. Compress Vertically Use this option to delete vertical space by moving the items upward. For example, consider three items, A, B, and C placed vertically. You can use this function to bring items B and C closer to the item A. To move items B and C upward, create a selection rectangle below the item A and select this option. The height of the selection rectangle specifies the upward movement of items B and C (noted that the selection rectangle does not need to include all items to be moved). All items below the selection rectangle are moved. This option also shrinks (vertically) the current section by the height of the selection rectangle. Field Menu: This menu contains options to insert, modify, delete and maintain fields.

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Modify: This option is used to modify the user prompt, width and prompt order of a dialogue field. The prompt order determines the order at which the dialogue fields are presented to the user for data input. Delete: This option is used to delete a dialogue field from the dialogue field table. You can not delete a dialogue field which is being currently used in the report. Section Menu: This menu contains commands to insert, edit and delete report sections. New: This option is used to create a new section. A section is identified by the section banner and the separation line at the bottom of a section. There are three basic types of sections. A header section displays the data that remain constant or changes only when a sort field changes. The detail section displays the transaction record fields. A footer section is used to display totals and summary information. ReportEase allows up to 9 header and footer sections. A higher numbered header section is allowed only when all the lower numbered headers are already selected. Similarly, a footer section is allowed only when the corresponding header section is already selected. Edit Current: This option is used to modify the properties of the currently selected section. For the 'detail' section, you can specify the number of records to print across the page. This option can be used to print multiple address labels across the page. Sort Field: This option is used to specify a sort field for a header section. A sort field is used to sort the data records. Break Field: This option is used to specify a break field for a header section. The break field is used to determine a sort break. Typically, the break field would be the same as the sort field. However you can specify the break field differently from the sort field. You can also specify a calculation expression for a break field. Filter: This option is used to enter a filter criteria to print a section. Normally, every section included in the report template is printed in its appropriate sequence. However, if you wish to print a section depending upon a condition, you can enter this condition expression using this option. The expression must evaluate to a logical value (TRUE or FALSE). During the report execution, the section will be printed only if the expression evaluates to a TRUE value. Line: This menu contains commands to create and edit a line object: Create a Line: Use this option to draw a line. When you select this option, the form editor displays a positioning rectangle. Use the mouse to position the rectangle and click any mouse key. The line will be drawn within the position rectangle. The line size can be changed using the sizing tabs. Edit Current Line: Use this option to edit the angle, colour, and thickness of a 'line' type object.

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Label: This menu contains commands to create and edit a label object: Create a Label: Use this option to create a new label. When you select this option, the form editor displays a positioning rectangle. Use the mouse to position the rectangle and click any mouse key. The 'label' object will be created within the positioning rectangle. By default, the form editor inserts the text 'label' in the label item. The label text can be edited in the editing window. Edit Current Label: A label text can be edited by simply selecting the desired label item and clicking on the edit window. As you insert or delete the text, the length of the label text changes. Normally, the form editor will automatically adjust the item box boundaries to completely enclose the new text. However, this automatic size adjustment ceases if you manually resized the item boundary by pulling on the sizing tab. This feature can be used to enclose the text in an item box larger than the default size. Picture: This menu contains picture import functions: Import Picture from Clipboard Use this command to copy a picture bitmap from the clipboard. When you select this option, the form editor creates a positioning rectangle equal to the dimensions of the picture. Use the mouse to position the picture rectangle and click any mouse key. The picture will be placed within the position rectangle. The picture size can be changed using the sizing tabs. Import Picture from Disk File Use this command to read in a picture bitmap from a disk file. When you select this option, the form editor creates a positioning rectangle equal to the dimensions of the picture. Use the mouse to position the picture rectangle and click any mouse key. The picture will be placed within the position rectangle. The picture size can be changed using the sizing tabs. Arrange: This menu contains commands to align, size and space a set of selected objects: Alignment At:

Horizontal Top Edge: Use this option to horizontally align the top edge of the selected items to the top edge of the leftmost item in the selection. Horizontal Bottom Edge: Use this option to horizontally align the bottom edge of the selected items to the bottom edge of the leftmost item in the selection. Horizontal Centre Line: Use this option to align the horizontal centre line (imaginary) of the selected items to the centre line of the leftmost item in the selection. Vertical Left Edge: Use this option to vertically align the left edge of the selected items to the left edge of the topmost item in the selection. Vertical Right Edge:

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Use this option to vertically align the right edge of the selected items to the right edge of the topmost item in the selection. Vertical Centre Line: Use this option to align the vertical centre line (imaginary) of the selected items to the centre line of the topmost item in the selection.

Even Spacing:

Horizontally: Use this option to place the selected items horizontally at an equal distance from each other. The inter-item distance is equal to the distance between the first two leftmost items. Vertically: Use this option to place the selected items vertically at an equal distance from each other. The inter-item distance is equal to the distance between the first two topmost items.

Even Sizing:

Width: Use this option to change the width of the selected items to the width of the topmost item. Height: Use this option to change the height of the selected items to the width of the leftmost item.

Undo Previous Arrangement Command

Use this function to undo the previous arrangement command. Report Executor Commands The report executor allows you to view reports which have been generated and saved to a native format file. It is invoked by using the view option from the reporting main window and selecting a file from the file selection box. The file selection box will point to the default data directory and will have the filter extension set to the correct file type (.FR). Figure 10.7 File Selector

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Figure 10.8 Report Executor

The options available on this window are:

Jump: Go to a particular page in the document. Print: Send the document to the defined printer. Preview: Look at the page layout of the document. Save: Save the document to a file (native and RTF). Exit: Quit the current window.

11 Plotting This section describes the reporting options and procedures used in the PVT plotting functions. 11.1 The Plot Display Plotting is available in many forms and is initiated by the plot command button option on many input and calculation screens. The plot window can also be removed by using the File|Close menu option, typing Alt +F4, or pressing on the exit button. The plot window contains may options which can be selected via a menu or toolbar. These options are details in Plotting – Menu and Toolbar section (11.1.3). A plot can present data form multiple stream calculations, allowing the user to visualise the effect of different compositions,matching scenarios etc.The plot below shows the variation in liquid dropout of samples taken at different depths. Figure 11.1: Plot Example Liquid Dropout

11.1.1 Manipulating Streams Clicking on the small square to the side of the stream name allows the user to manipulate the plotting of the stream Clicking on this square brings up a small menu as shown below:

Clicking on Hide Stream will change all the curves belonging to this stream to the background colour, hiding it. The Show Stream option returns the stream curves to view.Individual curves can also be hidden using the curve menu described below.


Clicking on Change Colour brings up the colour selection menu. Figure 11.1.1: Plot Example Liquid Dropout

11.1.2 Manipulating Curves On each plot is a set of small squares which indicate values from which the plot was derived. Passing over a square with the mouse pointer brings up a small window which gives the stream name and the point value. Figure 11.1.2: Plot Example Liquid Dropout

Clicking on Hide Stream will change the individual curve to the background colour, hiding it. The Show Stream option returns the stream curves to view.All streaml curves can also be hidden using the stream menu described above.

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Chapter 11 - Plotting 3 - 10

Clicking on Change Colour brings up the colour selection menu.: Clicking on Point Settings allows the user to adjust the size and number of the points shown for each curve in a stream. Selecting this option brings up the small dialog shown below:

The Plot Point Ratio indicates what fraction of the points will be displayed. The example above would show only one point in ten. To show all points enter a value of one. The Point size radio buttons allows the user to adjust the size of the Point Square. All point drawing can be switched off and on. See Labels and Options Dialog (Section 11.2.2) PLOT TITLE This may be adjusted if required . See Labels and Options Dialog (Section 11.2.2) MAIN PLOT WINDOW The main Plot window shows the curves drawn in engineering units. LEGEND BOXES Various legend boxes give additional information Note the legend boxes and the plot labels can be switched off within the Labels.. dialog. MOUSE POSITION INDICATOR A mouse position indicator (bottom right of main plot) which shows the current position in the units of the plot. This function can be used to find the value of an intermediate point on any drawn curve. Figure 11.1 and 11.2 show 2 typical plots. ZOOMING Any part of the plot can be enlarged by adopting the following procedure

1. Place mouse pointer at top left of the area to be enlarged. 2. Press the left mouse button down. 3. With the mouse button kept down , move the mouse pointer to the bottom right of

the required area. During this operation, a rectangle will be drawn to show the area selected.

4. Release the mouse button . The enlarged plot will be drawn. To return the plot to its original size , double-click the mouse anywhere within the main plot area.

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11.1.3 The Plot Menu and Toolbar The plot window is composed of : MENU with SUBMENUS 1) File

Printer Setup standard Windows Printer Setup display Print Exit 2) View

This menu allows the user to adjust what is seen within the display. Clicking on the menu item will toggle off and on the particular option. The options are stored on a file by file basis. 3) Display

Scales Set the axes scales Labels Set the Axes Label and Plot Title Text Variables Select the variables to be plotted Colours Select the colours of the various Plot Elements and sets pen size Test Points ..Mearured points to be visualised but not necessarily matched to. Units Change the Units used within the plot Redraw the plot at its original size.

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4) Output Report Bring up the main Report Display TOOLBAR

A toolbar with buttons for

font colour Units Scales Labels Help Exit

and with many plots combo boxes which give access to plot variables. Figure 11.2: Plot Example Phase Envelope

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11.2 Plot Menu Options 11.2.1 File The file submenu contains: Printer Set-up Clicking on this option invokes the windows standard printer set-up screen as described in Chapter 3. Print This option brings up the dialog shown in figure 11.3. Figure 11.3: Print Plot

The margin area allows the user to enter top, bottom, left, and right margins. The units of margin size can be selected using the Inches and Millimeters radio buttons. The listbox on the right of the display shows the printers available , with the current choice of destination highlighted. To select another printer , click once on its name. A small panel with radio buttons gives the user the opportunity to select between the three main colour schemes i.e. Monochrome, Greyscale or Colour. Line Widths : It may be useful when printing a plot which may subsequently be faxed to increase the line width This can be done via the Colours option within the main display The control buttons on the display have the following functions: Print Close the display and print report with current settings via the standard print control dialog shown below


Cancel Close the display without printing the report 11.2.2 Display The Display submenu contains: Scales To change the scaling of the plot click on this option, enter the values required in the Change Scales display (figure 11.4) and press OK. The plot will be redrawn automatically. Figure 11.4: Change Scales

Labels To change the labels and title used within the plot click on this option, enter the labels required in the Change Labels display (figure 11.5) and press OK. The plot will be redrawn automatically.

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Figure 11.5: Change Labels

Clicking off the Show curve labels on plot will remove the small curve labels. Clicking off the Show legend boxes on plot will remove the legend boxes, increasing the size of the main plot. Clicking off the Show Reference Data Lines will remove the indication of reference depth, reference pressure and reservoir temperature. Clicking off the Show Individual Plot Points will remove the small squares on the curves which represent actual values (see Main Plot Dialog section 11.1 for more details). Colours This option has the same result as that described for clicking on the Colours.button within the toolbar (see section 11.3) Units This brings up the unit selection display in a similar way to the main menu Options|Units option (see section 3.4). Redraw Selecting this option redraws the plot window. 11.2.3 Output The file submenu contains: Report This option brings up the user report window as described in Chapter 9.

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11.3 The Toolbar Options As a standard the plot window toolbar contains 3 control buttons which have the following functions Fonts... This option allows the user to change the fonts used in the plot. Figure 11.8 shows a typical fonts choice display. Figure 11.8: Plot Fonts

This screen allows the user to select a font for each of the text plot elements listed. First select a plot element by clicking on a name in the list, then use change button to choose the text characteristics that you require. An example of your choice is given in the dialog panel. Clicking on OK will change the font in the plot being viewed and close down the selection window . Pressing Apply will change the plot without closing the window. Colours Clicking on the Colours. Control Button or on Change Colour within the small point or stream menu (section 11.1) or on the Colours Option within the Main Plot Dialog Display Menu brings up this dialog. Figure 11.8: Plot Colours

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This option allows the user to change the colours used in the plot and set the default for all new plots. This screen allows the user to select the colour for each of the text plot components listed. First select the colour scheme to be applied to the plot i.e. Colour, Gray Scale or Monochrome. Next select a plot component by clicking on a name in the list. The sample panel will show the current colour. Press change to bring up the standard color selection dialog shown below. Choose the colour that you require and press OK. The sample panel will show your choice. The line width can also be set up on this display . To change a line width press on the required check box and press OK. Thicker lines are useful when printing out plots particularily for Fax use. Clicking on OK will change the colours in the plot being viewed and close down the selection window. Pressing Apply will change the plot without closing the window. Clicking on Save Colours will save all the colour selections to disk to be applied as default to all new plots.

12 Utilities This menu gives the user access to a series of utilities designed to help with general PVT work and to validate PVT report data The menu includes: API/Density Calculator Mass Balance Calculator Enthalpy Balance Calculator Hoffmann Quality Plot

Figure 12.1: API Calculator

12.1 API/Density Calculator This small dialogue is selected via the Utilities menu (see fig 12.1). To calculate an oil density from an API: Enter the API in the edit box and press Calc To calculate an API from an oil density from an API: Enter the oil density in the edit box and press Calc The units of density displayed can be changed using the units dialog.


12.2 Mass Balance Calculator This display is called from the main Utilities menu. The objective is to provide a tool which helps to validate PVT report Black OIl data. The calculation does not use any Equation of State model, it works only on the mass values within the dialog. If a report is consistent the mass of fluid removed at the reservoir should tally with the mass of gas plus oil at the surface. The calculator comes in 2 forms depending on the reservoir fluid OIL Using the basis of 1 stock tank barrel, it is possible from the stock tank oil density GOR and gas gravity plus the equivalent separator data to calculate a total mass of gas and oil associated with this volume of production. Similarily from the oil FVF and density, we can calculate the equivalent mass of this barrel of oil at reservoir conditions. If the two masses are not very similar then there is an inconsistency in the reported results which must be further investigated and eliminated. To carry out this calculation

1) Set the fluid to OIl using the radio button provided 2) Enter the reservoir, sparator and tank data required.

3) Select Validate using the mode radio button.

4) Click on Calculate.

If all the data has been entered correctly , the program will show the masses calculated for surface and reservoir plus the percentage difference between them.

Figure 12.2: Mass Calculator

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Chapter 12 - Utilities 3 - 9

Calculate Missing Value This mode is useful if a key piece of Black Oil data is missing. Enter all the data as above and press calculate. The program will assume the mass at surface and reservoir are equal and fill estimate the missing value. If more than one piece of data is missing an error message will be generated. A typical display would be that shown in figure 12.2 GAS In a similar way to that described for oils, the data from a gas or condesate can be used to constuct a mass balance between surface and reservoir. Unfortunately , most condensate reports do not have enough information to do a full balance. Instead the program uses the data entered and assumes the masses are equal. With the data provided, it calculates a series of values for gas FVF, density and molecular weight which can be validated against report or EoS calculated numbers. Two gas FVFs and gravities are reported . The first or dry value assumes that all the reservoir gas ends up as gas at surface. The real value follows from the mass balance and takes into account the gas that turns to condensate.

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12.3 Enthalpy Balance Calculator This type of calculation is called from the main Utilities menu. The aim of the utility is to predict the change in temperature if a fluid is moved from one pressure to another adiabatically.The temperature change is due to thermodynamic effects only as no heat is allowed to transfer to or from the system. The calculation comes in 2 forms a single or ranged multiple type. 12.3.1 Single Point Enthalpy Balance The inputs to the dialog are: Initial temperature

Initial Pressure and

Final Pressure

When these values are entered and Calc is pressed, the program flashes the fluid at initial conditions and finds the total enthalpy of the system. The program then iterates the temperature and flashes at the new T and P until the total enthalpy is within 0.01% of the initial value. During iteration intermediate values are shown in the right hand side of the dialog. When a successful match is found the process stops and the value is transferred to the results panel at the bottom of the dialog. A combo box is provided to select any stream within the PVTp file. (see help on STREAMS). A typical display would be

Petroleum Experts


12.3.2 Multiple Point Enthalpy Balance The aim of the utility is to predict the change in temperature if a fluid is moved from one pressure to another adiabatically.The temperature change is due to thermodynamic effects only as no heat is allowed to transfer to or from the system. The inputs to the dialog are: Initial temperature Initial Pressure and and either a range (auto mode) or a series of Final Pressures.(user selected mode). Auto Mode

1. Enter a Start Temperature and a Start Pressure. 2. Enter a minimum and maximum end pressure and the number of pressure values

required. 3. Press Calc.

PVTP User Guide


User Selected Mode

1. Enter a Start Temperature and a Start Pressure. 2. Enter a series of end pressures. 3. Press Calc.

Petroleum Experts


12.4 Hoffmann Quality Plot This display is called from the main Utilities menu. The principles behind this utility are described in the paper: Equilibrium Constants for a Gas-Condensate System by A. E. Hoffmann, J. S. Crump and C.R. Hocott, Trans.,AIME(1953)198,1-10. The basis of the plot is that if log(KP) is plotted against a characteristic b function the resultant values should approximate to a straight line. Any gross deviations from this behaviour suggest that the X, Y combination for that component is suspect. A typical data entry and calculation dialog is shown below. This display is called by selecting the Hoffmann Quality Plot option from the Utilities menu. Normally the table is blank but if data is present all the table values are automatically filled in when the dialog is loaded. The required entries are a set of matching vapour and liquid compositions at a known temperature and pressure. As each component percentage is entered a running total and remainder (100 - total) will be displayed. Mole fractions can also be entered. In this case, when Calc is hit the user will be prompted to auto correct the values. Where no value is available zero may be typed or a blank left. In the latter case the blank will be written automatically as zero.

When all component values have been entered, enter the temperature and pressure at which the samples were taken. Clicking on the Calc button will fill in the table as shown below.

PVTP User Guide


Click on Plot to bring up the typical graph. The plot shown below uses a set of values from the original paper. It can be seen that the values follow a rough straight line. To help visualising this effect, the program draws a straight line on the plot. The user can alter the position of this line by clicking on and dragging the handles at the either end of the line.

Petroleum Experts


PVTP User Guide

13 User Databases This section describes the setup and use of user databases. A Database menu has been added to the main PVTp screen. The dialogs within this allow the user to create and maintain a set of customised component databases. In addition an import facility has been added to extract components from the petroleum experts or other user-created databases. The databases can therefore be made up of entirely new components or existing components with some properties adjusted. The user database points are held within an ASCII file with a UDB extension. The directory where these files are stored is saved within the Prosper.ini file. This directory can be set using the Set User database Directory button which calls the User Database Directory Dialog. Once created , the databases can be used via the Select Components Dialog. Figure 13.1: Using database

If any *.UDB files exist their names will be displayed in the combo box provided. If the file has been created with user data, but the specific UDB file is not on the users machine the components will be listed within the user area for identification but cannot be extended or reset to the original *.UDB values. See example in figure 13.2


Figure 13.2: Database not present

13.1 Creating a User Database Figure 13.3: Creating database

This dialog is called from the Database Menu. The dialog allows the user to create an empty user database file (extension . UDB) and go on to add components via the database edit and database import dialogs. A typical display is shown in figure 13.3: The procedure followed ia as follows: Enter the database name and either select Exit and Save to create an empty file or Edit DataBase to begin populating the file with components (see User Database : Edit Dialog). The Set User Database Directory button brings up the User Database:Directory Dialog which sets up where the file will be stored.

Petroleum Experts

Chapter 13 - User Databases 3 - 6

13.2 Selecting a User Database Directory Figure 13.4: Selecting database directory

This dialog is called from the Select Components dialog and from the various user database screens. The dialog shown below allows the user to brows for a directory where the user database files (extension . UDB) reside. Selecting Browse will display a directory selection tree. When the selection has been made click on OK to store the data within the prosper.ini file.

PVTP User Guide


13.3 Editing a User Database Figure 13.5: Editing database

his dialog is called from the Database Create Dialog or from the Database Menu. The feature allows the user to add or remove componets from a user database. The properties of each component can be adjusted manually or calculated. All the data is read from and saved to an ASCII *.UDB file. A typical display is shown in figure 13.5 The minimum amount of data required is a short name (16 characters) , a long name (50 characters) and a molecular weight.The Fill in Values option will give reasonable values for all missing data based on several criteria , starting with molecular weight.All fields can be edited. The main control fields are as follows: Figure 13.6: Editing database 2

This allows the user to select the database to be edited.The Set User Database Directory button brings up the User Database:Directory Dialog which sets up where the file is stored.This area also contains a field which indicates the version of database by giving when it was last edited. Figure 13.7: Editing database 3

Petroleum Experts

Chapter 13 - User Databases 5 - 6

These combo boxes allow the user to select which correlations are used to determine the propertie sif required of the larger species within the database. The same correlations are used within the Pseudo Properties Dialog.

All changes are saved to the database file and the dialog is closed.

All changes are ignored and the dialog is closed.

All table entries are cleared.

As indicated above this option allows the user to fill in any properties with reasonable values based on the component's molecular weight etc.

This option brings up the Database Import Dialog. Within this display the user can select components from any other user database or from the Petroleum Experts database to import into the database being constructed. The p[roperties can then be adjusted within the edit database dialog.

PVTP User Guide


Petroleum Experts

13.4 Importing into User Database Figure 13.8: Editing database

Within this display the user can select components from any other user database or from the Petroleum Experts database to import into the database being constructed. The properties can then be adjusted within the Edit Database Dialog. A typical display would be as shown in figure 13.8. The left hand area of the dialog allows the user to select any of the Petroleum Experts components. To the right the user can call up any predefined user database and select components for import. When all selections have been made click on Exit and Save to import the values. The Set User Database Directory button brings up the User Database:Directory Dialog which sets up where the file is stored.

14 Preferences This section describes the options available from the Preferences section of the main PVT menu The magor option is called: Adjusting the Equation of State Calculation Tolerences Figure 14.1: Calculation Tolerences


14.1 Adjusting the Equation of State Calculation

Tolerences Selecting the Calculation Tolerences option from the Preferences menu produces the font selection screen shown in Figure 13.1 This Option is called by clicking on Calc. Tolerences within the Preferences Menu. These variables are normally set to the default values and should not be changed for the majority of systems. The values are stored along with each file allowing the user to customise them on a file by file basis. A flag is available to switch on and off the advanced phase detection on a file by file basis. Running with this check on is more secure with problem fluids but there is a considerable penalty in speed. The Phase Determination numbers below refer to the advanced method. The following variables are available for change: Phase Determination: Maximum Iterations (default value 500) There is a phase determination function which is used throughout the Equation Of State Calculations. The function starts at a high pressure and goes down in steps until a two phase area is detected. This value limits the number of steps allowed before the function is stopped with a single phase at all pressures assumed. Increasing the value will slow down the PVT calculations. Phase Determination: Minimum Pressure Step (default value 0.5) There is a phase determination function which is used throughout the Equation Of State Calculations. The function starts at a high pressure and goes down in steps until a two phase area is detected. This value limits the smallest allowed step before the function is stopped with a single phase at all pressures assumed. Decreasing the value will slow down the PVT calculations.Increasing the value may cause phase changes to be missed. BUT Library Initialisation:Number Of Iterations (default value 60) The BUT Library is at the core of all the Equation Of State Calculations. This value controls the action of many programs within the Library , limiting the number of times a solution is sought in any particular subroutine.Adjusting this value will have an indeterminate affect on the systems accuracy and performance. BUT Library Initialisation:Degree Of Precision (default value 3) The BUT Library is at the core of all the Equation Of State Calculations. This value controls the action of many programs within the Library ,limiting the accuracy sought in any particular subroutine. If a more precise solution is required the value should be increased. Adjusting this value will have an indeterminate affect on the systems accuracy and performance. Regression : Maximum Number of Steps (default value 20) This value relates to the number of regression cycles which will be done before the calculation automatically exits. Raising the value will allow more time for a slowly

Petroleum Experts

Chapter 14 -Preferences 3 - 3

PVTP User Guide

regressing system to find a solution . No upper limit has been set , but any value lower than 10 will be set to the lower allowed limit of 10. Regression : Intermediate Gradient Steps (default value 10) The compositional Gradient is a stepwise process. When a target depth is entered for regression , the program must insert a series of intermediate depths to get a meaningful result. More steps normally means a more accurate estimation. The disadvantage is a much lower cycle time for regression. 10 steps represents a reasonable compromise value.

Appendix A - Worked Examples

A1 Example 1 - EOS calibration of oil sample using PVTP. “The aim of this exercise is to demonstrate how the PVT Package can be used to build an equation of state (EOS) model for an oil sample. Even though the current example deals with oil, the steps outlined is applied to any other type of hydrocarbon system.” The objectives of this example are: • To familiarise the user with building EOS models in PVTP. • To use PVTP to calibrate the EOS models to measured laboratory experiments. • To generate PVT tables for various applications. This example will take the user through the following steps: Building an EOS Model • How to set up a PVTP model • How to enter the composition of the fluid • How to characterise the heavy ends • How to define the binary interaction coefficients Calibrating the EOS Model • How to match the saturation pressure • How to match the separator results • How to match the constant composition expansion results. Using PVTP to Generate tables • How to generate black oil tables for MBAL • How to generate black oil tables for PROSPER. • How to generate black oil tables for Eclipse • How to generate the EOS input data for PROSPER. This example is in the samples directory under “ samples/pvtp/example1.pvi” Input Data Reservoir Fluid Composition

Component Mole Percent

N2 0.05 CO2 0.15 C1 37.6 C2 9.7 C3 9.8 C4 6.6 C5 4.3 C6 3.5 C7+ 28.3

Reservoir Data:

2 - 57 Appendix A - Worked Examples

Producing Interval Depth 10000-10050 feet Reservoir Pressure 4000 psig Reservoir Temperature 199.4 degF

Saturation Pressure Data

Saturation pressure at 199.4 degF: 2800.0 psig Separator Data A multi stage separator experiment performed on the reservoir fluid resulted in the following results:

Stage Pressure (Psig)

Temp. degF GOR (scf/stb)

Oil Density (API)

#1 500 90 500 #2 0 60 300 34.2*

*34.2 API = 853.953 kg/m3 Constant Mass Expansion Experiment results: The results of the constant mass study at done of the sample at 199.4 degF are:

Pressure in psig Oil Viscosity (cP) Oil Density (Kg/m3)

Psat 2800 0.470 693.60 3100 0.495 697.55 3400 0.520 701.20 3700 0.542 704.66 Pres 4000 0.565 707.96

Petroleum Experts

PVTP User Guide 3 - 57

A1.1 Step-by-step approach to building an EOS model in

PVTP 1. Defining the System Options The first thing that needs to be defined is the options. For the selections of the right options, you click on |Options |Options and then select the following options.

Figure A.1.1: Options Input Screen

In this screen, we are indicating that we will use EOS modelling and the EOS we will use is Peng Robinson. You hit on OK to complete this.

i) You can also model fluid behaviour as a Black Oil in PVTP. ii) The other Equation of State that is available is the Soave Redlich

Kwong (SRK). You can also define a customised equation of state. 2. Units Selection in PVTP: The default Units System in PVTP is Oilfield Units. If you are using another set of units you will have to reset the units system. To do so click on Options |Units and then set the Input as well as the Output Units to Oilfield as done below:

i) You can set the whole set to another system like French S.I. ii) You can also change the units of a particular variable within a unit

system by clicking on the unit next to it and selecting a new unit from the list that is displayed.

PVTP User Guide


Figure A.1.2: Unit Selection Screen

3. Component Selection In order to select the components, you hit on Data|Select Components. To select components in the screen shown below click on the desired components. The selected ones will be highlighted. Once you finish the pure component selection, enter the number of pseudo-components in the bottom right hand corner of the screen.

Figure A.1.3: Component Selection Screen

i) You can un-select any selected component by clicking on it again. ii) We strongly recommend to start with a single pseudo.

Petroleum Experts


4. Entering the fluid composition On the previous screen once you defined the components, hit on Edit Composition which will bring up the following screen, where the compositions are entered as shown:

Figure A.1.4: Component Input Screen

On this screen, the reservoir conditions i.e., pressure temperature and depth at which the sample is taken are also entered. 5. Defining the Pseudo-Component The next step is characterising the C7+ component. Clicking on the Pseudo Props does this. Button of the above screen. This takes you to the following screen, whereby you enter the specific gravity and molecular weight of the C7+ component.

PVTP User Guide


Figure A.1.5: Pseudo-Component Entry screen.

The specific gravity entered here is 0.871 and the molecular weight is 275. On basis of these numbers, we calculate the boiling point and the Tc, Pc etc using the correlations.

Figure A.1.6: Pseudo-Property Calc.

Petroleum Experts


To do so press Calc Values on the previous screen. The correlations used are Petroleum Experts for boiling point and TWU / Edminister for critical properties. This thus calculates the pseudo-properties on basis of the correlations.

i) There is a utility called Quick Calc. In many input screens of PVTP,

which allows you to study the general model behaviour based on the parameters entered/ calculated do far.

ii) We have entered the compositions and calculated the Pseudo-properties from correlations. We can use this utility to see how this model will perform in terms of oil density predictions at surface conditions.

To do so on the above screen, hit the Quick Calc button. The following screen appears. On this screen, select the flash to Standard Conditions as shown.

Figure A.1.7: Quick Calc Screen.

Hit on Calc. On this screen, it gives the results of a single stage flash as shown below.

Figure A.1.8: Single-Stage Flash results.

PVTP User Guide


As can be seen from the calculation, with the current pseudo-characterisation, the oil density after flash using the equation of state modelling is 15 API, which is very different from the 32 API type oil we are getting. To get a pseudo, which does give correct liquid density computation, we use the feature called Automatch in PVTP. If we click OK on the previous screen, it will take us back to the following screen, where by, you press Auto Match button at the bottom left hand corner.

i) Experience has shown that the liquid densities predicted by

Standing and Katz method are always fairly close to the measured density under atmospheric conditions, as the method is based on the conservation of mass.

ii) Thus, during Auto Match, we iterate on the Heavy end parameters

until the EOS predicted density at surface is equal to the Standing and Katz density calculated at surface.

iii) This usually provides a good starting point for calibrating the EOS

models further. iv) During automatch, the difference between the two density values is

displayed as well. Ensure that this is small as automatch stops after 40 iterations. If the difference is still large, press automatch again to perform 40 more iterations. Usually 40 iterations are enough.

Figure A.1.9: Using Auto Match

Petroleum Experts


Once automatch is done, using Quick Calc. again gives the following results for a single stage separation.

Figure A.1.10: Single-Stage Flash results. After Automatch

The density calculated now is much more reasonable and very near what we have in the laboratory reports. To come back to the Pseudo-Property input screen click on OK. Once the pseudo is acceptable, it is recommend to save this information in a archive. To do so on the Pseudo-input screen click on Store button on the bottom right hand side as shown in figure A.1.9. To view the stored data click on View on the same screen. You should see the following information stored.

Figure A.1.11: Stored Pseudo-Properties

6. Defining the Binary Interaction Coefficients Once the pseudo component has been characterised, the next step is to introduce binary interaction coefficient between the components. To do so, from the Pseudo-property screen figure A.1. 9 click on Exit and save. This takes you to the component input data screen, which is figure A.1.4. On this screen click on B I Coeff. Button. This takes you to the following screen, where you can define the binary interaction coefficients.

PVTP User Guide


Figure A.1.12: Stored Pseudo-Properties

i) You need to enter only the lower part of the full BI matrix. We have

used only 0.05 between the C1 and pseudo in this case. ii) You can also use the correlations for calculating theses values, by

hitting Calc. New Values. iii) There are also two Reset buttons at Top which allow you to set

specific (pure/ all components) values in the matrix to zero.

To see the effect of introduction of Binary interaction coefficient on the saturation pressure, we can again use the Quick Cal. Utility that appears on this screen as well. If we press on Quick calc. and then select phase envelope on the screen shown in figure A.1.7, the following phase envelope appears.

Petroleum Experts


Figure A.1.13: Phase envelope with Quick Calc.

To see the impact of the binary interaction coefficient on saturation pressure, click on Set Test Point on the above screen and enter the saturation pressure data as shown below

Figure A.1.14: Entering saturation pressure data point.

i) Ensure that you have selected the data point to be plotted on the

phase envelope as indicated at the bottom of the above

PVTP User Guide


Once this is done we can click on OK to take us back to the Phase envelope screen as shown in figure A.1. 13. On this we can click on Expand he plot to see the whole plot. We can see, the data point (shown as the blue +) with respect to the phase envelope as well.

Figure A.1.14: Phase envelope versus measured saturation pressure data point.

i) The EOS model we have at this stage is not respecting the fluid

behaviour as seen in the laboratory data. The fluid behaviour at this step is strictly governed by the PR equation of State and Tc, Pc etc., data entered.

ii) To make the EOS model to replicate the fluid behaviour as seen in

the laboratory, we need to calibrate/ match the EOS model. iii) Also Note that PVTP has indicated that the system is a bubble

point system, without the user having to define it using the in built advanced phase detection algorithm.

Press Exit on the graph to come to Quick Calc screen in figure A.1.13, click Exit on this screen to go to screen shown in figure A.1.7. Click Cancel on this screen to come to BI Coeff screen shown in figure A.12.Press Exit and Save on this screen to save the data input. This takes you to the component input screen shown in figure.A.1.4. Click Exit and save on this screen and this take you to the main PVT screen. At this stage you can save the file by going to File | Save as and the following screen appears. You can browse to the directory you want to save the file in and save it there.

Petroleum Experts


Figure A.1.15: File Saving Dialogue

This finishes the data entry of for building the EOS model.

PVTP User Guide


A1.2 Step-by-step approach to Calibrating an EOS model in

PVTP

1. Entering the measured data The first step is entering the measured laboratory data. To do so, in the main PVTP screen, go to Data | Enter Lab Data, and this will give the following screen. Enter the known data in the relevant sections as shown:

Figure A.1.16: Entry of saturation Pressure

To enter the CCE click on the CCE tab that appears on the screen shown above in figure A.1.16 and this takes you to the next screen, where the data is entered.

Petroleum Experts


Figure A.1.17: Entry of CCE data

Similarly enter the separator experiment data under SEP tab in the lab data screen as shown

Figure A.1.18: Entry of Separator data

2. Selecting the Data to calibrate against/ match to Once the data is entered, we can again save the file as described earlier. To select the data points that will be used in calibration, we will do the following

Disabling data points

PVTP User Guide


The first step we take is to disable some data points in CCE density and viscosity measurements to which the model will be matched to. To do so from the main Menu click on Data | Enter lab data and select the CCE data tab as shown. On this select the both columns of oil density and viscosity by holding the down the mouse and dragging across the cells you want to disable. This selects the cells. Once the cells are selected, click on disable. This disables the data, i.e. the data will not be used for matching.

Figure A.1.20: Disabling Lab CCE data

i) The disabled data is shown in grey shading. ii) A good model with predictive capabilities should use the

minimum data to calibrate and should predict other observed behaviour within reasonable accuracy.

The next step is to include minimum data from this elaborate experiment and match the EOS to it. We will select the density and viscosity at reservoir pressure and bubble point. Selecting the data point by clicking on it to make the cell active does this. Once the cell is active, click on include to include the data. You can also browse the weighting and select a number e.g. 5 and hit set weighting to set weighting of data in the active cell /cells to 5.

Petroleum Experts


Figure A.1.21: Enabling Lab CCE data / Setting weighting

i) The enabled data is with a white background. ii) The low weighting cells appear in blue compared to black for the

high weighting cells iii) We will give a medium weighting to density and viscosity at

reservoir conditions.

3. Matching the properties except viscosity Once the properties that need to be matched against are selected, click OK to get out of lab data entry screen. In the main Menu Click on Data | Regression and the following regression screen appears. On this screen select all the data except viscosity for regression.

i) Note that you will need to scroll down to select all that against

which you will regress the model. ii) Ensure that viscosity is not selected as a regression variable at this

stage of matching.

PVTP User Guide


Figure A.1.22: Selecting the data for regression.

Click on Regress on this screen. This takes you to the next screen, where the parameters that will be altered to match to lab data are chosen. Chose the Tc, Pc data of all components except for the non-hydrocarbons and the binary interaction coefficient between heavy fraction and methane, as indicated below and hit Regress.

Figure A.1.23: Selection of Parameters to be varied in regression.

Once the regression is done, there automatically appears the following screen showing the tuned properties of all the components.

Petroleum Experts


Figure A.1.24: Tuned EOS parameters.

On this screen, click on Exit and Save. It takes you back to the regression screen figure A.1. 23. On this screen click on Exit and save and it takes you back to the regression data selection screen as shown in figure A.1. 22.

4. Matching viscosity. Once the rest of data has been matched to, viscosity is matched separately. To do so un-select the other parameters in the following screen and select viscosity only as shown

Scroll down the list to ensure that no other property except for viscosity is selected for regression.

PVTP User Guide


Figure A.1.25: Selecting viscosity for regression.

Once this is done in a similar fashion, go to the next screen by clicking on Regress and only select the Pseudo-component critical volume for fine-tuning. Make sure that no Tc, Pc, omega, binary interaction is selected as shown in the screen below

Figure A.1.26: Selection of Vc of Pseudo to match viscosity.

Once the matching is finished, the same screen as figure A.1.24 appears. Click on Exit and save on this screen. This takes you to the regression screen on figure A.1.23. On this screen press Exit and Save and it takes us to main regression screen shown in figure A.1.22. On this

Petroleum Experts


screen click on PVT Main and this takes you to the main PVT screen., where you can save the data and the results.

5. Checking results of the calibrated model against lab data. Once the model is calibrated, we need to check the model predictions against the lab data. The first comparison is the CCE experiment. To simulate a CCE experiment in PVTP, from the main menu go to Calculation | Constant Composition Expansion and the following dialogue box will appear, where the range of pressure and temperature is entered.

Figure A.1.27: Setting up CCE Simulation input.

If we are also comparing oil FVF and GOR etc, we need to enter the separator scheme that these values were calculated against in the CCE data. If we leave it blank all the GOR and FVF values reported in the simulated experiment assume single stage atmospheric flash.

On this screen Press on Calc. This takes you to the next screen as shown below. On this screen press Calc. again and the CCE calculations are performed.

PVTP User Guide


Figure A.1.28: Simulated CCE Results.

Once these calculation is finished, hit on plot and a plot will be displayed. On this plot select, pressure versus the oil density (EOS) to be displayed. The selection is on the top of the plot in the drop down menu as shown in the figure below:

Figure A.1.29 Simulated CCE versus lab oil density Results.

Petroleum Experts


On the same plot a comparison of oil viscosities looks as given below.

Figure A.1.30 Simulated CCE versus lab oil viscosity Results.

Similarly other experiments like phase envelope, separator tests can be simulated and checked against the measured data. This concludes the EOS calibration stage.

A1.3 Using PVTP to generate Tables for other applications

1. Black Oil tables for Petroleum Experts The Black Oil tables for Petroleum Experts Applications are generated by going to File | Export from the main menu. This will result in the following dialogue screen to appear.

Figure A.1.31 Black Oil Export Dialogue Screen.

On this screen hit OK. This takes to the next screen, where the table pressures and temperature is defined as shown below:

PVTP User Guide


Figure A.1.32 Black Oil Export Dialogue Screen.

i) You may also copy the CCE simulation experiment in the table to

be exported by clicking on copy CCE button shown on the screen. ii) You may define tables at ten temperatures. iii) You need not enter the saturation pressure for the table, PVTP will

calculate it automatically. iv) On the right hand side Select, the table type, i.e., whether oil, gas or

condensate.

As the table contains GOR and oil FVF information as well, you need to define a separator train for this case. In case we do not define a separator train and atmospheric single stage flash is considered. In this example we will define the separator train similar to the one used in lab data. To do so on the above screen, click on Set Up under separator conditions and the following dialogue appears,

Figure A.1.33 Defining separator set up for black oil table

Petroleum Experts


On this screen enter the separator scheme. Click Use Separator to calculate GOR and oil FVF. Once this is done click on OK and it takes you back to the Export screen shown on Figure A.1.32. On this hit Calc. Table button. If you have more than one table selected for export, hit Calc. all. This populates the table with PVT data as shown below. Once the table is filled, on the right hand side press MBAL select. This selects the columns to be exported.

Figure A.1.34 Populated Black Oil table

On this click on Export and it will come up with the following dialogue

Figure A.1.33 Black Oil table Export

On this screen select current table option as we have only one table. Click on Export and it takes to the following screen, where we can save a *.ptb file, which can be read by Petroleum Experts applications.

PVTP User Guide


Figure A.1.33 Black Oil table Export

At the end of this step you have a black oil table that can be used. 1. Black Oil tables for Eclipse The Black Oil tables for eclipse are generated following the same route as was followed for Petroleum Experts Applications. We start from File | Export from the main menu. This will result in the following dialogue screen as shown in figure A.1.31 to appear. On this screen select table Type 6 which is Eclipse Black oil Tables and hit OK.

This takes us to the following screen. On this screen, you have to select the type of black oil tables that are needed.

Figure A.1.34 Eclipse Black Oil table Export

Petroleum Experts


i) First you define the type of phase tables you want. In this case we

want a oil with dissolved gas, the gas being dry and no water type tables.

ii) Based on the phase types selected, applicable keyword Options become available. We are using PVTO and PVDG for this example.

Once the proper options are selected, click on OK. This takes you the following screen, where you define the pressure and temperature range for which the tables need to be generated.

You also define the separator scheme that will be used to calculate the GOR and oil FVF values.

Figure A.1.35 Eclipse Black Oil table Export, Pressure and Temp. Range Input

Once the data is input, click on Export and it takes you to the following screen, where the tables are displayed. Click on Calculate to populate the tables.

PVTP User Guide


Figure A.1.36 Eclipse Black Oil table

Click on Export on the populated tables and it takes you to the save screen as shown below.

Figure A.1.37 Eclipse Black Oil table saves

You can save the table as a *.inc file which can be used by Eclipse. Click on PVT Main to come back to the main screen.

2. EOS input for PROSPER The EOS input tables for PROSPER are generated following the same route as was followed for the other two cases. We start from File | Export from the main menu. This will result in the following dialogue screen as shown in figure A.1.31 to appear. On this screen select table Type 1 which is PROSPER EOS Composition and hit OK. This takes us to the following screen. On this screen, you have to select the appropriate option

Petroleum Experts


Figure A.1.38 EOS Export for PROSPER

Once the option is selected, click on Export and it appears with a saving screen and as in figure A.1. 37. Select the name for the file and it saves a *.prp file which can be imported directly into PROSPER.

PVTP User Guide


A2 Example 2 - EOS calibration of a Condensate Sample using PVTP

This objectives of this example are: • To familiarise the user with using the Advanced Pseudo-Splitting Option in PVTP • To use PVTP to calibrate the EOS models to measured laboratory experiments. • To perform wax and hydrate studies on the condensate sample This example will take the user through the following steps: Building an EOS Model • How to characterise the heavy ends using the advanced splitting method. Calibrating the EOS Model • How to match the saturation pressure • How to match the separator results • How to match the constant composition expansion results. Simulating Experiments • Study the calibrated EOS for wax appearance temperatures • Find wax amount • Perform hydrate formation study • Work out hydrate inhibitor concentrations. This example is in the samples directory under “ samples/pvtp/example2.pvi” Input Data Reservoir Fluid Composition

Mole Percent Component

0.31 N2 2.33 CO2

68.73 C1 12.37 C2 5.01 C3 2.71 C4 1.4 C5 0.96 C6 6.18 C7+

Petroleum Experts


Reservoir Data:


Saturation Pressure Data

Saturation pressure at 199.4 degF: 4800.0 psig Separator Data A multi stage separator experiment performed on the reservoir fluid resulted in the following results:

Stage Pressure (Psig) Temp. degF GOR (scf/stb) Oil Density (API)

# 1 500 100

(


A Note about Liquid Dropout

i) There are two common ways of reporting the liquid drop out in

laboratory reports: • As a % of the cell volume at dew point pressure. • As a % of cell volume itself.

ii) In the PVT Package, the dropout as % of the cell volume is to be entered.

iii) If the lab reports the dropout as % of the dew point volume, this has to be corrected. These reports also have a column called relative volume in the reported in the CCE experiment.

• By definition the relative volume dew

cellr V

V=V

rV = relative volume

cellV = Total volume of the cell at given P,T

dewV = Volume of the cell at the dew point pressure iv) Thus to get liquid dropout as % of cell volume, we divide the liquid

dropout number expressed as % of dew point volume by the relative volume.

Petroleum Experts


A2.1 Step-by-step approach to building an EOS model in

PVTP 1. Defining the Condensate System

i) The first is defining the options, selecting the components, and

entering the composition as is indicated in the step by step approach of example 1. The steps are exactly same.

ii) You start with one C7+ component and go through automatch etc

as indicated in example 1. The specific gravity is 0.8 and the molecular weight is 180.

2. Splitting the heavy end. Once the pseudo is characterised and automatched, we are at the following screen as shown.

Figure A.2.1 Pseudo-Input Screen

On this screen press the Advanced button on the Split option at the bottom of the screen.

If you have more than one pseudo defined in the above screen, the advanced splitting is applied to the last pseudo only.

The advanced splitting dialogue takes us to the following screen on which using the internal splitting algorithms, a distribution with carbon numbers of C7+ components is constructed as shown.

PVTP User Guide


Figure A.2.2 Advanced Splitting Screen

i) For estimating the distribution of C7+ carbon numbers for a given

system, there are various options available. ii) Petroleum Experts2 is the default option, which constructs an

extended distribution starting from C7 in such a way that the average molecular weight and specific gravity of C7+ we started with are honoured and as the carbon number increases, the mole fraction decreases.

iii) There is also the Petroleum Experts 1 and Original method, both of which calculate the extended distributions in such a a way that the distributions tend to be centred around a particular carbon number.

iv) In case the user knows the individual mole fractions of the higher carbon number, the follow profile method can be selected, which will cause the split to be along the mole% profile entered by the user.

The plot of the distribution with Petroleum Experts2 Method is shown below. This can be done by pressing Plot on the above screen.

Petroleum Experts


Figure A.2.3 Heavy end profile with Petroleum Experts 2

If we want to choose the Petroleum Experts 1 as the splitting method, we click on Exit on the above graph, which takes us to screen shown on figure A.2.2. On this select Petroleum Experts1 and press Recalculate split. Once this is done hit again on plot.

Figure A.2.4 Heavy end profile with Petroleum Experts 1

As indicated in above plot, this distribution is centred around C13 and thus has a maximum there.

For this case we will use the default one i.e. Petroleum Experts 2. To switch back to it follow the same sequence as was followed to construct Petroleum Experts1. Once this is done, we will split this profile into two sub-groups by hitting on Set Even Split as shown in the following screen.

PVTP User Guide


Figure A.2.5 Splitting the Pseudo

Once this is done, the program splits the heavy end into two groups, one from C7-C12 and another C12+. If the user wants to change the range of carbon numbers in the sub-groups, it can be done by scrolling up and down on the C13-C35 group.

Once the sub-groups are defined, click on Automatch. Once automatch is done, introduce a binary interaction coefficient of 0.05 between C1 and C13+ by clicking BI Coeff on the above screen as shown

Figure A.2.6 BI Coeff. Entry

Click on Exit and save and it takes you back to the screen on figure A.2.5. Click again Exit and Save through all the screens, till you are again in the main PVTP screen. On the main screen save the file.

Petroleum Experts


A2.2 Calibrating an the EOS model in PVTP The first step is entering the measured laboratory data. To do so, follow the steps exactly similar to example 1. From the main PVTP screen, go to Data | Enter Lab Data, and this will give the following screen. Enter the known data in the relevant sections as shown:

Figure A.2.7 Lab. Saturation Pressure Entry

Figure A.2.8 CCE. Data Entry Screen.

PVTP User Guide


Figure A.2.9 Separator Data Input

Once the laboratory data is entered, we will disable, set weighting to the various options as indicated below. To do so we will follow the same steps as indicated in example1.

i) All liquid drop data except 9.86%, which is the highest number, and

5.51%, which is at 4500 psig, are disabled. The 5.51% has medium weighting.

ii) The Z factor at dew point is included with high weighting. iii) The saturation pressure is included. iv) The first stage GOR and last stage density in separator

experiments have high weighting. The other GOR values have low weighting.

Once this is done we go to the regression screen following the same steps as in example 1 and select the properties as follows

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Figure A.2.10 Regression Data Input

After selecting regression properties click on Regress and this takes us to the screen below. Chose the Tc, Pc data of all components except for the non-hydrocarbons and the binary interaction coefficient between heavy fraction and methane, as indicated below and hit Regress as was done in example 1

Figure A.2.11 Regression Screen

This finishes the calibration of the EOS model to the laboratory data.

PVTP User Guide


A2.3 Checking results of the calibrated model against lab

data. Once the model is calibrated, we need to check the model predictions against the lab data. The first comparison is the CCE experiment. To simulate a CCE experiment in PVTP, from the main menu go to Calculation | Constant Composition Expansion and the following dialogue box will appear, where the range of pressure and temperature is entered.

Figure A.2.12: Setting up CCE Simulation input.

If we are also computing oil FVF and GOR etc, we need to enter the separator scheme that these values were calculated against in the CCE data. If we leave it blank all the GOR and FVF values reported in the simulated experiment assume single stage atmospheric flash.

On this screen Press on Calc. This takes you to the next screen as shown below. On this screen press Calc. again and the CCE calculations are performed.

Petroleum Experts


Figure A.2.13: Simulated CCE Results.

Once these calculation is finished, hit on plot and a plot will be displayed. On this plot select, pressure versus the liquid dropout to be displayed. The selection is on the top of the plot in the drop down menu as shown in the figure below:

Figure A.2.14 Simulated CCE versus lab liquid dropout Results.

This concludes the PVT calibration step.

PVTP User Guide


A2.4 Simulating PVT Experiments in PVTP In this section we will use PVTP to simulate the following experiments: 1. Wax appearance modelling

PVTP has the capacity to model, the temperatures at which wax starts to appear in the fluid. It also has calculation routines, which work out the wax weight and mole percent and the number of phases that are formed.

To access wax appearance calculations, from the main PVTP screen, go to Calc. Solids options. Under this option select wax appearance temperature calculation. Once done the following screen appears

Figure A.2.15 Wax appearance temperature Input data.

There are various methods available for calculating wax appearance temperature. We have selected the Pederson wax method. The pressure range over which the temperature is to calculated is specified as well. Next we hit calculate and the following screen appears. On this screen click on Calc. to start the calculations

Petroleum Experts


Figure A.2.15 Wax appearance temperatures

In this case the calculations show that for all the pressures the wax appearance temperature is around 70.2344 F

To calculate the amount of wax that deposits, click on PVT main on the previous screen. This takes us to the main PVTP screen. On the main screen go to Calc. Solids options. Under this option select Wax Amount calculation. Once done the following screen appears

Figure A.2.16 Wax amount input dialogue

There are various methods available for calculating wax appearance temperature. We have selected the Pederson wax method. The pressure range over which the amount is to

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calculated is specified as well and so is the temperature of 70 F. Next we hit calculate and the following screen appears. On this screen click on Calc. to start the calculations

Figure A.2.17 Wax amount

This table gives the amount of wax that is formed. It also indicates the separation of the original fluid into various phases.

Petroleum Experts


2. Hydrate and hydrate inhibitor modelling. PVTP has the capacity to model, the hydrate appearance pressures. It also has calculation routines, which work out the minimum inhibitor concentrations required to suppress hydrate formation.

To access hydrate appearance calculations, from the main PVTP screen, go to Calc. Solids options. Under this option select Hydrate Formation Pressure calculation over a range of temperatures and a couple of inhibitor concentrations. Once done the following screen appears

Figure A.2.18 Hydrate appearance Pressure Input data.

There are various methods available for hydrate formation pressures prediction. We have selected the Kihara Potential P.E.H. method. The temperature range over which the pressure is to calculated is specified as well. Next we hit calculate and the following screen appears. On this screen click on Calc. to start the calculations

PVTP User Guide


Figure A.2.20 Wax appearance temperatures

In this case the calculations show the minimum hydrate formation pressures for a range of temperatures and inhibitor concentrations.

To Plot the results press Plot and the following plot appears.

Figure A.2.21 Hydrate formation plot

Hydrate Region

From the plot we can see that as the temperature and inhibitor concentration increase, the hydrate formation pressures go up also and you need higher and higher pressure to form hydrates. Click Exit to come out of the plot and click on PVT main to come to the main PVTP screen.

Petroleum Experts


A3 Example 3 – Estimating Decontaminated sample properties of an contaminated Oil Sample using PVTP

This objectives of this example are: • To familiarise the user with the decontamination procedure that can be used in PVTP This example will take the user through the following steps: Building an EOS Model • How to make the C7+ distribution in PVTP follow the carbon number versus mole% profile

measured in laboratory. Decontaminating in PVTP • Step by step approach to estimate the uncontaminated sample properties from a

calibrated EOS model of a contaminated oil sample.

This example is in the samples directory under “ samples/pvtp/example3.pvi”

Input Data

All the input data including the sampling is on a contaminated oil sample. The experiments like CCE, bubble point determination, etc were performed on the contaminated sample.

Contaminated Reservoir Fluid Composition

Component Mole Percent

N2 0.05 CO2 0.15 C1 37.6 C2 9.7 C3 9.8 C4 6.6 C5 4.3 C6 3.5 C7+ 28.3

PVTP User Guide


Reservoir Data:


Saturation Pressure Data of the Contaminated sample

Saturation pressure at 199.4 degF: 2800.0 psig Separator Test Data of the Contaminated sample A multi stage separator experiment performed on the reservoir fluid resulted in the following results:

Stage Pressure (Psig) Temp. degF GOR (scf/stb) Oil Density (API)

#1 500 90 500 #2 0 60 300 34.2*

*34.2 API = 853.953 kg/m3 Constant Mass Expansion Experiment results on the Contaminated sample: The results of the constant mass study at done of the sample at 199.4 degF are:

Pressure in psig Oil Density (Kg/m3)

Psat 2800 693.60 3100 697.55 3400 701.20 3700 704.66 Pres 4000 707.96

Petroleum Experts


Extended Composition analysis of the C7+ fraction contaminated Reservoir Fluid sample

C7 0.5413 C25 0.17 C43 0.0534

C8 0.5076 C26 0.1594 C44 0.05

C9 0.476 C27 0.1494 C45 0.0469

C10 0.4463 C28 0.1401 C46 0.044

C11 0.4185 C29 0.1314 C47 0.0413

C12 0.3924 C30 0.1232 C48 0.0387

C13 0.3679 C31 0.1155 C49 0.0363

C14 13.165 C32 0.1083 C50 0.034

C15 1.0926 C33 0.1016 C51 0.0319

C16 3.0245 C34 0.0952 C52 0.0299

C17 0.9606 C35 0.0893 C53 0.028

C18 2.9007 C36 0.0837 C54 0.0263

C19 0.2501 C37 0.0785 C55 0.0247

C20 0.2345 C38 0.0736 C56 0.0231

C21 0.2199 C39 0.069 C57 0.0217

C22 0.2062 C40 0.0647 C58+ 0.0203

C23 0.1933 C41 0.0607

C24 0.1813 C42 0.0569

PVTP User Guide


A3.1 Step-by-step approach to decontamination in PVTP 1. Defining the Contaminated System You can match the contaminated oil sample following the steps exactly in the same fashion as listed in example1. At the end of this you have a matched EOS model for the contaminated oil.

The starting point for this example is that we have matched an equation of state for the contaminated oil based on the laboratory tests as indicated. The pseudo C7+ has been characterised.

2. Setting up the C7+ profile as per measured data To do so from the main PVTP screen go to the pseudo input data screen. To do so Click on Data | Edit Composition | Pseudo Props. and it takes us to the following screen.

Figure A.3.1 Pseudo- Property input screen

On this screen, click on the Advanced option and it will take you to the next screen whereby PVTP generates a mole % profile for C7+ using the default method.

Petroleum Experts


Figure A.3.2 Advanced Pseudo- Property screen

On this screen, we want to enter the profile, we have measured in the laboratory. To do so, click on Set up Split Profile button and the following dialogue comes up. Fill the measured mole% data against carbon number in the screen.

Figure A.3.3 Setting up Profile

PVTP User Guide


Once the profile has been set-up, click on Exit and Save and it takes you back to the advanced split screen. On this screen press Recalculate Split as shown below.

Figure A.3.4 Recalculating the Profile

Once this is done click on Exit and Save on all the screens that appears till you come to the main PVTP screen. 3. Decontaminating the sample Once the heavy end profile has been defined, from the main menu go to Data | Decontaminate. This takes you to the decontamination input dialogue as shown below

Figure A.3.5 Decontamination Input Dialogue

Petroleum Experts


This screen lists all the components along with their mole %, molecular weights etc. The C7+ components are listed in red.

The next step is to remove / re-estimate the excess mole % of heavy end hydrocarbon that comes from the contaminant. For this example we will try to estimate the contaminant mole % from the heavy end profile. If we click on Plot on the previous screen, it gives the following plot.

Figure A.3.6 Carbon number Vs Mole %

The initial peak that is seen in the profile is because of C1 which is as expected. To see the profile after C7 we can hold down the mouse button and draw a box around the area and it results in a following zoomed plot.

Figure A.3.7 Carbon number Vs Mole %

Now after C7 the profile naturally is expected to be smooth as we had seen in example 1. The peaks that we see in the profile from C14 to C18 are due the contamination from the oil based

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mud. From this plot assuming a uniformly decreasing smooth curve the mole % of the C14-C18 can be estimated. The estimated mole percent are

Component Old Mole Percent Estimated Mole

Percent C14 13.165 0.323 C15 1.0926 0.298 C16 3.0245 0.286 C17 0.9606 0.280 C18 2.9007 0.269

In case you know the exact composition of the contaminating fluid and contamination weight %, this can easily be converted into excess mole % of that component. The excess mole % can be subtracted out of the system and new mole percent estimated in the second column

Once the new mole percent are estimated, these are entered in the decontamination screen as shown below

Figure A.3.8 Decontamination Procedure

Once new compositions are entered, press on Quick Look. This takes us to the next screen where the program creates a temporary decontaminated stream and we can quickly look at its properties

Petroleum Experts


Figure A.3.9 Decontamination Quick Calc.

On this screen press again Quick Calc. It takes us to the next screen as shown Figure A.3.10 Decontamination Quick Calc.

At this stage PVTP has created a temporary decontaminated stream called Decon_Temp and we can perform the listed calculations on it. Begin by selecting Phase envelope and pressing Calc. This takes us to the following screen. On this screen, on the left hand side all the fluid streams are listed. Select both the contaminated and decontaminated one and hit Calc.

PVTP User Guide


Figure A.3.11 Phase Envelopes

This picture shows how the phase envelopes compare. Because of decontamination the saturation pressure goes up in this case. Click on Exit | cancel | Exit and it takes you to the screen in figure A.3.8. On this screen click on Decontaminate, which take us to the following screen.

Figure A.3.12 Decontamination

On this screen you get two options. One in which you can create a new stream in the file with the decontaminated fluid model or you can overwrite the contaminated one. We choose to add a new stream. After this press Decontaminate and the program calculates the decontaminated fluid model and displays the EOS parameters of the same as shown below

Petroleum Experts


PVTP User Guide

Figure A.3.13 EOS Parameters of the Decontaminated sample

Enter Exit and Save on this and subsequent screens to go to the main PVTP screen. At this stage you will have a decontaminated fluid model.

Appendix B Step by Step Guide

This section describes the steps which can by followed to characterise a fluid with the PVT Package. This route will be successful in all but the most difficult cases. The information here is repeated in the form of help (PVTSTEP.HLP). This help is available from the Help Menu on the main PVTP display. B1 List of Steps Step 1: Create a New ( Section B.1) Step 2: Select Equation of State Options ( Section B.2) Step 3: Select Components ( Section B.3) Step 4: Enter Composition ( Section B.4) also see Sample PVT Report Composition ( Section B.4.1) Step 5: Initialise the Pseudo Component Properties ( Section B.5) Step 6: Match the Surface Volumetric Properties (Density, GOR etc.) using the

Automatch feature ( Section B.6) Step 7: Use Pseudo-Splitting or BI Coefficients to get near Reservoir Saturation

Pressure Value ( Section B.7)

also see Using BI Coefficients ( Section B.7.1) Using Pseudo Splitting ( Section B.7.2) Step 8: Select Match Parameters ( Section B.8) Step 9: Use Regression to Match Fluid ( Section B.9) Step 10: Check and Refine the Fluid Characterisation ( Section B.10) Step 11: Calculate, Report and Export ( Section B.11)

2 - 30 Appendix B - Step by Step Guide

B1.1 Step 1: Create a New File

Create a new file by selecting the New command., from the File menu. This can be done at any time. See also: File/New (Section 3.1)

Petroleum Experts

Appendix B - Step by Step Guide 3 - 30

B1.2 Step 2: Select Equation of State Options

or use icon Part of a typical display is shown below :

The program will default to the most commonly used combinations i.e. ♦ 1 Method set to Equation of State and ♦ 2 Equation of State set to Peng Robinson Clicking on OK is enough to move on to the next step More detail on alternative entries is given in Options (Section 5.4 )

PVTP User Guide


B1.3 Step 3: Select Components

or use icon A typical display is shown below :

Petroleum Experts


The important selections are : ◊ 1 Choose the required components by clicking on the names within the listbox. The

number of components depends on the application and the information available within the PVT report. See Sample PVT Report Composition. The Reservoir or Wellstream analysis will contain a list of components up to C6, C10, C12, Cxx etc. The plus fraction should have associated with it a Molecular Weight and a Specific Gravity. This information is required to characterise the Pseudo Component(s) in Step 5 Normally, selecting up to C6 and having a C7+ pseudo is enough for all oils and most condensates.

◊ 2 Enter the number of Pseudo Components (normally 1) and ◊ 3 Click on Edit Composition to proceed to next step NOTE: The difference in properties between normal and iso butane and normal and iso

pentane do not warrant there inclusion as separate components. The program will run faster if nC5 and iC5 are lumped together under the nC5 label. Similarily, with nC4 and iC4 should be lumped as nC4.

More detail on alternative entries is given in database Selection (Section 7.1)

PVTP User Guide


B1.4 Step 4: Enter Composition

or use icon

but normally the display is loaded using the button on the Select Components page (Step 3) A typical display is shown below

Petroleum Experts


Enter the composition in mole % from the Reservoir or Wellstream analysis for each component (1) and pseudo component (2).See Sample PVT Report Composition (Section A.4.1). A running total of the entries is displayed (3). At this point reference data , especially the temperature at which the sample was taken, should be entered in area 4. This temperature will be used to conduct the Saturation Pressure calculations within Step 7 When all entries are complete click on Pseudo Props.. (5) to move on to the next step. More detail on alternative entries is given in Edit Composition (Section 7.2)

PVTP User Guide


B2 Sample PVT Report Composition

HYDROCARBON ANALYSIS OF SEPARATOR PRODUCTS TO AND CALCULATED

WELLSTREAM

TO HEPTANES PLUS AND CALCULATED WELLSTREAM

SAMPLES Separator Separator Wellstream Component Liq. Mole % Gas Mole % GPM Mole % --------------------------------------------------------------------------------------------------------------- Hydrogen sulphide 0.00 0.00 0.00 Carbon dioxide 0.16 0.90 0.50 Nitrogen 0.01 0.32 0.15 Methane 6.02 77.97 38.87 Ethane 4.94 12.58 3.364 8.4 Propane 6.53 5.51 1.518 6.06 i-Butane 1.45 0.56 0.183 1.04 n-Butane 4.84 1.38 0.435 3.26 i-Pentane 1.97 0.22 0.080 1:17 n-Pentane 3.35 0.29 0.105 1 95 Hexanes 4.81 0.15 0.058 2.68 Heptanes plus 65.92 0.12 0.053 35.89 Totals 100.00 100.00 5.796 100.00 Heptanes plus properties Molecular weight : 225 103 (assumed) 225 Density at 600F (gloc) 0.8527 0.7370 (assumed) 0.8526 API at 600F Cg/cc) 34.3 34.3 Important Information 1 Individual component compositions 0.00.....2.68% and C7+ pseudo composition 35.89% 2 Pseudo Component (C7+) molecular weight 225 and SG 0.8526

Petroleum Experts


B2.1 Step 5: Initialise the Pseudo Component Properties

At least one pseudo component should have been identified in step 3. After the pseudo percentage(s) have been entered in step 4 , click on the Pseudo Props. button to display to bring up the important Pseudo Properties Display A typical display is shown below:

The purpose of this step is to give the pseudo component(s) an initial set of properties. The pseudo is the greatest unknown within the composition and is always composed of a mixture of many compounds with a wide variety of individual properties. It is therefore, not surprising that the characterisation of these compounds is the key area of EOS PVT matching. The starting values for Tc, Pc , AF etc. are taken from correlations. Normally the PVT report will give SG and Molecular Weight information for the plus component. See Sample PVT Report Composition Section A.4.1). . Enter the values in the table (1). The

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correlation(s) will calculate a Boiling Point and use this with SG and Mwt. to fill in the other properties (2). The default correlations are Petroleum Experts for BPt. and Twu/Edminster for Tc, Pc , AF . Clicking on Calculate Values(3) or exiting the pseudo properties dialogue will initiate the property estimation. Choice of Correlation The correlation can by changed by using the combo boxes in area (4) Our recommendation for this selection is : ⇒ For All Fluids , try 1. Petroleum Experts Correlation for Boiling Point 2. TWU/Edmister for Acentric Factor etc. NOTE : The properties of the pseudo(s) will only be recalculated if the Boiling Point value for that pseudo is blanked out.

The mode (5) should normally be set at Automatic. Manual mode assumes the user will type in all the properties. When the initial properties are in place, the user should move on to step 6 for further pseudo characterisation. More detail on alternative entries is given in Pseudo Properties (Section 7.3)

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B2.2 Step 6: Match the Surface Volumetric Properties (Density, GOR etc.) using the Automatch feature

Automatching is the key to efficient fluid characterisation within the PVT Package Background The Equation of State model is not ,at present, predictive. This weakness leads to the need for extensive fluid matching. In addition, the model is particularly poor at estimating liquid densities. The combination of these factors leads to an overall picture of an equation with many variables ,many component properties and therefore many routes to matching a complex fluid over a range of pressures and temperatures. If an efficient route is not taken, it can be very difficult to resolve the overall picture especially with regard to reservoir and separator densities. Since all volumetric oil properties FVF GOR etc. are derived from density it is critical that this area is accurately modelled. What is Automatching Within the PVT package two liquid densities are calculated by two different methods. The first is based on an empirical correlation from Standing and Katz. The second is calculated from the Equation of State liquid compressibility. Experience has shown that the Standing and Katz value which is derived mainly from specific gravities is always fairly close to the measured density at surface conditions. The Automatch process involves a series of flashes at 60 degrees F and 1 atm with an adjustment to the pseudo properties after each flash. The aim is to bring the EOS density in line with that calculated by Standing and Katz. The boiling point (s) of the pseudo(s) are adjusted after each iteration and the other properties recalculated using the new value. Figure 1 illustrates the result of Automatch on a typical oil

The effect of Automatching is to move the lower end of the phase envelope into a realistic area giving close to the correct values for separator oil density GOR FVF etc.. The matching of this area becomes minimal ,allowing the overall regression to move more

PVTP User Guide


smoothly to a solution. In general, the top end of the phase envelope is little changed for oils during Automatch . With condensates, the Saturation Pressure may become depressed enough to require remedial action i.e. splitting (see Step 7) How to Automatch Automatching is a very straightforward process. Enter the Pseudo Properties Dialogue as described in Step 5. A typical display would be :

Simply click on the Split in 2 button . Split into two each time . Check the effect on the Saturation Pressure after each split (see Step 7) A feature is provided within the program to store and restore pseudo component data. The program will automatically store the first entries in this dialog. The Restore can be used to undo a split if the Saturation Pressure becomes too large. If this method proves to be unsuccessful more control over the Split by using the Advanced function. See also Decontamination Procedure(Apendix B) NOTE: Automatch is not suitable for gases as it depends on liquid being formed When Automatch is complete proceed to Step 7 More detail on alternative entries is given in Pseudo Properties (Section 7.3)

Petroleum Experts


B2.3 Step 7: Use Pseudo-Splitting or BI Coefficients to

get near Reservoir Saturation Pressure Value The aim of this step is to assist the package to smoothly find the reservoir fluid Saturation Pressure. The aim is to use various techniques to get in the proximity(within 5%) of the correct value. The regression mechanism can then be used to match the value exactly. When Step 6 is complete and the Pseudo Properties Dialogue is exited , the program will be showing the Edit Composition Dialogue as shown below.

All the operations required for this step are available within this dialogue. Make sure a reference temperature is entered at point 4 After each operation the saturation pressure can be found by clicking on the Calculate button at point 1. This brings up the Small Calculation Dialogue :

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Select Saturation Pressure and press Calculate to bring up the message box containing the result:

Petroleum Experts


This is a general guide. Special cases may require a different approach ⇒ CONDENSATES Condensates can be much more difficult to match than oils. The calculated Saturation Pressure can be initially very far from the match value. The use of B I Coefficients is not as effective in this area. Introducing the coefficients change the shape of the phase envelope as well as inflate it. The shape change may, in some cases, result in a decrease in Saturation Pressure at the reservoir temperature. Splitting the pseudo component is recommended for condensates as the effect is larger and spread more evenly across the phase envelope. Close to the required value one or two BI coefficients (between C1 and the heaviest components) can be used to move the value a little. The proposed sequence is :

Petroleum Experts


B2.3.2 Using BI Coefficients Figure 2 shows the effect of adding Binary Interaction Coefficients to a real condensate example. This pattern of behaviour is commonly found.

Adding the coefficients moves the phase envelope from values depicted by curve B to those making up curve A. Although there is an increase in saturation pressure over most of the temperature range e.g. T1, the envelope tends also to tilt leaving some areas with a lowered PSat. e.g. T2. In this example ,there is negligible movement at the reservoir temperature leaving the match point PSat as far away as before. Adjusting BI Coefficients is not recommended for condensates other than making up small (<10%) differences between calculated and match PSat values. Splitting the last pseudo component is the preferred option with condensates which exhibit the behaviour shown above. See Using Splitting to Match Saturation Pressure (Section A.7.2) Oils , in contrast, can benefit from adding BI coefficients. The saturation pressure is normally closer to the initial calculated value and the phase envelope range is normally like that of T1 in figure 2. Splitting with oils also tends to give an excessively high value which cannot be easily brought back by regression. Where the difference between the calculated and match values are small the difference can be made up by manually adjusting the BI Coefficient(s) of C1 with the heaviest component(s).This value has the greatest influence on the saturation pressure calculation

Petroleum Experts


Adjusting Binary Interaction Coefficients Click on the BI Coeffs.. button within the Edit Composition (Section 7.2) to display the Binary Interaction Coefficients Dialogue. A typical example is shown below :

Any coefficient can be changed by clicking on a cell and typing in a new value. Use the combo boxes to give options on calculating a new set of values. Buttons are provided for zeroing all components, or those of the pure (non-pseudo) components. See BI Coefficients Dialog (Section 7.4) for more detail on the options available.

PVTP User Guide


B2.3.3 Using Pseudo Splitting Figure 3 shows the effect of Pseudo Splitting on a real condensate example.


Splitting the Last Pseudo Splitting is a very straightforward process. Enter the Pseudo Properties Dialogue as described in Step 5. A typical display would be :

Simply click on the Split in 2 button . Split into two each time . Check the effect on the Saturation Pressure after each split (see Step 7) A feature is provided within the program to store and restore pseudo component data. The program will automatically store the first entries in this dialog. The Restore can be used to undo a split if the Saturation Pressure becomes too large. If this method proves to be unsuccessful more control over the Split by using the Advanced function. See also Decontamination Procedure(see Appendix B). Automatching should be done after each split (see Step 6) to ensure that surface properties are maintained. More detail on alternative entries is given in Pseudo Properties(Section 7.3)

PVTP User Guide


B2.4 Step 8: Select Match Parameters Why Match? The Equation of State model is not predictive. Without matching, the equations will work mathematically. Unfortunately, the results will ,in many cases, diverge greatly from the known characteristics of the fluid. Matching ties the model to real points in the PVT behaviour of the fluid, giving the equations less freedom to drift into unrealistic areas. What is the minimum data to Match ? An important principle to understand at this point is that the Equation of State does not respect the fundamental law of conservation of mass. Figure 4 illustrates why this may be a problem.


approach causes can be very significant and will come out in many ways e.g. in the inability to resolve reserves with production. To avoid such problems we recommend that reservoir and separator matching must always be done together Densities or density derived data must be included for reservoir and surface to force a material balance on the system. NOTE The EOS calculation initially calculates Zliquid and Zvapour. Densities are calculated directly from the Zs. Matching Z matches density The recommended minimum information to be used for matching is: ⇒ OILS 1 Bubble Point pressure 2 A measure of density (oil density or Zliquid) at reservoir or saturation pressure conditions 3 Some measure of Separator volumetric properties i.e. GOR or oil FVF 4 A measure of density (oil density or Zliquid) at separator or stock tank conditions ⇒ CONDENSATES 1 Dew Point pressure 2 A measure of density (gas density or Zvapour) at reservoir or saturation pressure

conditions 3 Some measure of Separator volumetric properties i.e. GOR or oil FVF 4 A measure of condensate density (oil density or Zliquid) at separator or stock tank

conditions 5 Liquid Dropout (CCE or CVD) from reservoir pressure to surface conditions B2.4.1 How is Match Data entered?

or use icon will bring up the match table dialogue. This consists of a series of tables one for each measurement/calculation. Any cell can be filled in with data. Blanks are allowed where data is not available or unreliable. Make sure all pressure steps are entered for SEP(Separator) and CVD(Constant Volume Depletion). Figure 5 6 7 and 8 illustrates the data used for a real condensate example.

PVTP User Guide


Figure 5 Saturation Pressure

Figure 6 : Zgas at reservoir and saturation pressures

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The value at reservoir pressure ensures that any deviation of compressibility above the dewpoint is properly modelled Figure 7 : Separator GOR and Stock Tank Oil Density

Note that all separator stages have been included as the final oil density depends on the path to Stock Tank conditions.. With multiple stage separators it is best to match first on the main stage. In addition, when GOR numbers are much smaller in the subsequent stages,it is unlikely that these values are as accurate. We suggest that a lower weighting.eg. 3 is given to these numbers. see help on Match Data Tables for Weighting and Inclusion/Exclusion.

PVTP User Guide


Figure 8 : CVD Liquid Dropout

The CVD process also includes all stages including the start point at the saturation pressure value. Missing out any stage will alter the values for all stages below it. There are many ways to approach dropout matching and no best way to do it. One thing to keep in mind is that the values are not as accurately measured as density or saturation pressure. For that reason the values should all be given a lower weighting e.g. 3. This prevents important numbers like PSAT moving to help dropout to match. It is also better not to start with all values included in the match. Give the program 2 or 3 representative points, match to them and view the result. If required include more points until a reasonable match is produced. See help on Match Data Tables(Section 7.8) for Weighting and Inclusion/Exclusion NOTE: for CCE dropout the values expected are relative to the volume at step not the volume at reservoir volume . Most PVT reports give dropout relative to reservoir. To convert the values devide the dropout figure by the relative volume at each pressure step. When all entries are complete click on OK to move on to the next step. More detail on alternative entries is given in MatchData Tables(Section 7.8)

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B2.5 Step 9: Use Regression to Match Fluid

or use icon Regression is a two stage process. In the first, the user must select which calculations should be matched. Selecting regression brings up the dialogue illustrated below:

Each column within the match table (Step 8) has an equivalent checkbox within this dialogue. It is recommended that all calculations with the exception of any CVD or GRAD variables should be selected at once. The total selected is displayed at point 4. Every calculation can be given a high , medium or low weighting which changes its contribution to the overall error. Unless the match value is suspect or of lower accuracy (e.g. a dropout), the weighting should be left as high. When the calculations have been selected, click on Regress... to move on to the next stage

PVTP User Guide


See Regression Match Data (Section 7. 8) for details on alternative selections. The next stage is to select the parameters to be used during regression. A typical Regression Parameter Dialogue is shown below :

Generalising a regression strategy is difficult. Fortunately,however, with the PVTP most oils and condensates can be matched in a single shot. When using a full composition , it is recommended that allTc Pcs should be selected for C1 and all components below. In addition, any binary interaction coefficients should also be selected. See What Properties to Use in Regression and Matching Viscosities for more information. Vc is only used when viscosity is being matched (see Matching Viscosities) Click on Regress to initiate the matching calculations. The process stops when a maximum number of steps has been passed or the error term CHI falls to below 1e-09.The process can be restated if not enough steps have been taken. If the regression fails to converge satisfactorily, more component properties can be added. See Regression for more information on options and strategies. When the first round regression has been completed more difficult variables such as dropout can be added and the process repeated.

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B2.6 Step 10: Check and Refine the Fluid Characterisation It is important to check and refine the model of the system. Use the calculation menu options to check the values produced for the match parameters. In addition , other non-matched parameters should be calculated and compared with the PVT report values to test the validity of the model. Remember that all the reported values will not be as of the same accuracy. For example, small dropout values are difficult to measure. Check the scatter of percentage dropout points using the Testpoints (Section 7.11) facility, prior to deciding the weighting of the calculation (Step 9) and which point(s) should be used for matching. If an oil or condensate does not readily match using the method outlined here , our experience has been that in many cases detailed investigation of the reported data has shown an inconsistency. The error normally lies in the area of sampling and handling . Compositional Gradient Matching a compositional gradient to fix a pressure or other variable with depth can be done See MatchData Tables (Section 7.9) for more information. This calculation is very important if a significant gradient is anticipated or if there is a gas - oil contact within the reservoir If modelling is to be done successfully, it is recommended that at least two sampled points should be available within the oil leg. The reason for this suggestion is that the gradient is a function of fluid density The variability in oil density with depth may not be well enough characterised with only one match point Splitting can Help Compositional Gradient Matching If matching a gradient becomes problematic, it is recommended that the Pseudo Splitting function should be tried. The Compositional Gradient calculation is done on the basis of a component's Molecular Weight. For the pseudos ,the individual species which will make up the component are changing with depth. This should be represented as a change in pseudo make-up and therefore Molecular Weight with depth. At present, however, within PVTP, the pseudo is represented as having a fixed composition with depth. Splitting allows the program to manipulate the new pseudos via their relative compositions to achieve the Molecular Weight change.

PVTP User Guide


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B2.7 Step 11: Calculate, Report and Export Characterising a fluid is not normally an end in itself. The aim is to make use of the model produced in a way that helps us to understand and predict the effect of the fluid's PVT on all aspects of its processing. The main uses include Calculating values not covered by well tests or laboratory measurements. Use the calculation menu options (Section 8) to carry out any of the many calculation options available with the PVT package. Utilising Phase Envelope (Section 8.2) function to visualise the behaviour of the fluid over a wide range of temperatures and pressures Export (Section 3.12) the characterised composition to Prosper for compositional nodal analysis (see Export /Prosper) Calculation of Black Oil properties which can by exported to Prosper ,MBAL etc. in the form of Black Oil Tables. This is particularly important for characterising condensates.(see Export/Black Oil Tables and General Export in Section 3.12) Use Gravitational Gradient (Section 8.9) to understand the changes of phase and composition with depth within a reservoir. This can in many cases explain what sometimes seems the unnatural behaviour of complex reservoirs. Connection between wells can be confirmed. Peculiar changes in GOR etc. with production can be explained. If the PVT of a reservoir is understood , everything else becomes clearer. Use the Extract (Section 8.3.1) function to sample the composition of the oil or gas which results from a process change (separator calculation) , reservoir depletion (CVD, DIFF or DEPL) or change of depth (GRAD) Reporting (Section 9) can be used to send compositions , regression information and calculation results in an organised fashion to printers, clipboard, or spreadsheets.

Appendix C Decontamination

Procedure NOTE This procedure represents one way of decontaminating a sample. It may not be applicable to all situations and the results cannot be guaranteed. The flexibility of the program also allows other paths to a solution to be followed. The object of this exercise is to identify the effects of a contaminant within a fluid and to remove this contamination in a controlled manner. What should be available is the characteristics of the contaminated fluid i.e. a PVT report an extended analysis of the contaminated fluid and an estimate of what the fluid composition would be without the contaminant

What we are going to do is a match to the known characteristics with a split history that reflects the addition of the contaminant. This is done by using the Split Profile feature. Matching gives the properties of the pseudo components and the split history identifies how they were put together. In the decontamination display the program breaks the matched fluid back down into the many split parts along with compositions and properties associated with each part. The user can then set the compositions to that of the uncontaminated fluid. When this is done the program adjusts the compositions and properties to reflect the change and recombines the split parts to workable pseudo components. This new working composition can be used to generate data for an uncontaminated model.

2 - 7 Appendix C - Decontamination Procedure

STEP 1 Follow the Step by Step Guide until you reach step 5. A single C7+ pseudo

component should be sufficient for most fluids.

STEP 2. Enter the pseudo component MWt and SG. within the Pseudo Properties page

and click on the Advanced button within the Split/Profile area at the bottom of the display.

STEP 3. Within the Advanced Splitting Dialog select the Follow Profile method using

the combo box provided above the table. click on the Setup Split Profile button.

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Appendix C - Decontamination Procedure 3 - 7

STEP 4. Within the Split Profile Dialog enter the detailed composition of the

contaminated fluid. Only the areas of strong contamination are required. The program will fill in the rest with a standard distribution. Click on Exit and Save.

STEP 5. Back within the Advanced Splitting dialog click on Recalculate Split to

implement the profile.

PVTP User Guide


STEP 6. It is possible to undertake the tasks described as step 6 (Auto matching) and

step 7 (getting near reservoir PSAT)within the Step by Step Guide within this display. Complete these operations now. this is preferable to exiting and coming back into the Advanced Splitting dialog . The reason is that Advanced in the Pseudo Properties Dialog applies to the last pseudo component. If splitting has been done, you must use Restore the Original Numbers to get back to your starting point. When you are happy with your entries click on Exit and Save.

STEP 7. The Stream now contains a set of partly matched pseudo components with a

full history of how they were put together. Continue to fully match this fluid as described in the Step by Step Guide .

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STEP 8 When fully matched, select Decontaminate from the Data menu. This brings

up the Decontamination Control Dialog. The compositions presented are based on the split history of stream. This will contain the profile created in Step 4. Click on Plot to view the component distribution. the properties of the expanded pseudos are derived form the matched pseudos. they therefore contain a measure of the effect of each expanded component on the overall characteristics of the fluid.

STEP 9 Enter the estimated values for the composition of the undecontaminated fluid

in the New Mole% column. this can be derived from the amount and composition of the contaminant and the original composition of the contaminated sample. Only the area of obvious contamination needs to be entered. Click on Plot to view the results. Click on the Quick Look button to view the effects of your entries. this option creates a temporary stream containing the decontaminated fluid.

PVTP User Guide


STEP 10. To complete the decontamination process click on Decontaminate. The

Output Selection Dialog which appears allows you to pick between using the existing stream or creating a new one. It would normally be better to create a new version as it allows your starting point to be kept for comparison and future reference.

STEP 11. On returning to the Decontamination Control Dialog the display will contain

information on the results of the decontamination. The decontamination calculation proceeds as follows: The individual component mole percents are set equal to the New Mole%

values , where defined. The remaining component mole percents are adjusted to make up the 100%

total and to follow the trend of the original values. The new full composition appears as the Cald. %. The Calcd% are used in conjunction with the initial properties to generate a new

set of properties for each component and a combined version for each of the pseudo components. The pseudo component start and end values can be seen by clicking on the View/Change button.

The trend in the individual compositions can be seen by using the Plot button.

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PVTP User Guide

STEP 12 The decontamination procedure is now complete. Click on Exit and Save and

then File|Save to store the results. STEP 13 An effort should be made to confirm the accuracy of the fluid model against

any other known properties of the reservoir fluid e.g. field separator data when it becomes available or the reservoir fluid density from RFT measurements.

Appendix D PVTP OPEN SERVER Manual

This Appendix describes the OPENSERVER features within PVTP 6. It is envisaged that this information will appear within the general IPM OPENSERVER manual in subsequent major releases. D1 Introduction This user guide is designed to explain how to use OPENSERVER to access PVTP from external programs. This document gives an overview of the uses of the OPENSERVER. It then gives full details of how to use the feature in PVTP. D1.1 About This Guide The guide assumes you are familiar with basic Windows operations and terminology. It also assumes you are familiar with PVTP. It would also be helpful if you are familiar with using VBA macros in Excel. The screen displays used in this guide are taken from the examples provided with the software. On occasion, the data files may vary from the examples shown as updates to the program are issued. Where major amendments or changes to the program require further explanation, the corresponding documentation will be provided. D1.2 What is in this guide Chapter 2, "Overview," summarises the OPENSERVER feature. It explains the

potential uses of the OPENSERVER and how it can be used with external programs. It should provide enough information to assess if the feature can be used to solve a particular problem without understanding the details of its operation.

Chapter 3, "Support," defines the responsibilities of Petroleum Experts with

respect to supporting the OPENSERVER. Chapter 4, "Using the OPENSERVER," describes the technical details of linking

external programs to Petroleum Experts products using the OPENSERVER. Chapter 5 PVTP and the OPENSERVER," describes the features specific to the

use of PVTP with the OPENSERVER

2 -37 Appendix D -–PVTP OPENSERVER Manual

D1.3 How To Use This Guide Read chapter 2 to gain an overview of the OPENSERVER feature. This should be sufficient to decide if the OPENSERVER can be used to solve a particular computing or technical problem. If you decide that the OPENSERVER may be of use, it is necessary to read chapter 4 to understand how to implement an OPENSERVER solution. D1.4 Symbols and Conventions Throughout the user guide, special fonts and/or icons are used to demonstrate specific steps, instructions and procedures in the program.

PETEX program The term PETEX program is used when the comment is applicable to MBAL or GAP.

ALL CAPS Represent DOS directories, file names, and commands. Italics Used to highlight certain points of information. Keycap Bold fonts are used to indicate a specific action to be taken.

For example: "Click Done to exit the window." Menu Command To avoid repeating the phrase "Click the File menu and choose the

Open command," we use the File - Open convention instead. ➲ Emphasises specific information to be entered or aware of.

Step-by step instructions are marked by this keyboard icon.

This symbol is a reminder to click the RIGHT mouse button. Clicking the right mouse button, performs specific functions in MBAL, depending on the active dialogue box or plot. If you do not have a right mouse button, holding down the SHIFT key while you click the mouse button performs the required function.


Appendix D - PVTP OPENSERVER Manuall 3 - 37

D2 Overview The OPEN SERVER feature is designed to provide an Open Architecture for Petroleum Experts products. This allows PETEX programs to be directly accessed and driven by other programs. Specifically, the OPENSERVER will allow other programs (such as Excel, programs written in Visual Basic) to access public functions in PETEX programs. These can then be accessed by an external program in an automated procedure. D2.1 Basic Functions There are a number of public functions that have been made available. However the three most important functions are as follows. D2.2 GetValue This function allows an external program to query a data value in a PETEX program. It should be possible to obtain the value of any data item that can normally be viewed using the user interface of the PETEX programs. Each data item is defined by a unique text string. D2.3 SetValue This function allows an external program to change a data value in a PETEX program. It should be possible to change the value of any data item that can normally be viewed using the user interface of the PETEX programs. It should be possible to build a data set from scratch using the SetValue function. However, it is recommended that the user interface is still used to build parts of a data set which do not require any automation. This will allow the normal quality checking to take place which is a very important aspect of the model building process. Each data item is defined by a unique text string. D2.4 DoCommand This function allows calculations to be performed in a PETEX program. Each calculation type is defined by a unique text string. Only a subset of calculations available via the normal user interface of the PETEX products are available using the OPENSERVER. In particular, the DoCommand function supports those calculations which are applicable to automated use e.g. a GAP prediction. However it generally does not support those calculations that require the user interface for correct use e.g. MBAL graphical matching.

PVTP User Guide


D2.5 Calling the Functions There are two methods of calling the public functions. The following sections describe the two methods. Note that these sections only summarise how to call the functions - the exact syntax is described in the Using OPENSERVER section (Section 4). D2.6 Automation The OPENSERVER feature can be accessed using Automation. This is a Microsoft Windows standard for communicating between programs. The OPENSERVER is an Automation server. This means that the public functions can be called from any program that can act as an Automation client. There are many programs that can act as an Automation client and can therefore be used to call the public functions in the PETEX programs. These include: Any VBA macro. These macros are available in Excel, Access and many other

Microsoft products. Visual Basic programs can be written to act as an Automation client and

therefore call the public functions. C++ programs can also be written to act as an Automation client and therefore

call the public functions. Many other products can act as Automation clients. Check their individual documentation.

D2.7 Batch File To avoid dependence on Automation, it is also possible to call the public functions in the PETEX programs using a simple batch file. The functions required are typed into a text file. A program is supplied by Petroleum Experts (PXBATCH) which will interpret the text file and call the functions in the PETEX programs. It also writes the output of the GetValue function to another text file which can be viewed afterwards.



D3 Potential Uses This section outlines some of the possible uses of the OPENSERVER. It is not an exhaustive list but should give some idea of its possibilities. D3.1 Batch Runs Consider a situation where you have set up a prediction calculation in MBAL. However it would be of interest to check the final recovery for a range of values for the original oil in place. You could create a spreadsheet in Excel which lists all the OOIPs that you want to try. Then write a VBA macro within Excel which:- Gets the first OOIP value from the spreadsheet and sets it in the MBAL tank Runs a production prediction Queries the final recovery from the production results and writes into the

spreadsheet. Repeat for the next OOIP and so on…

If there is a large number of OOIP values to try or the calculation is particularly slow, this macro could be run overnight. D3.2 Custom Reporting Although PETEX products provide a variety of report formats, it is possible that you require a specific layout for your reports. A VBA macro within Excel can be written to query the required values from a PETEX product and then written in the required format to the spreadsheet.

PVTP User Guide


D3.3 Data Import/Export The OPENSERVER can be used for transferring data to or from a database and PETEX programs. The client program can use any technique to access the values in the database (e.g. ODBC, DAO, SQL) and then transfer them with OPENSERVER. For example, if you have production data stored in an Access database, you can write a VBA macro in Access to query the data from the database and then use the OPENSERVER to set the data in the MBAL data set (an example of this is available in the installed MBAL examples – OPENSERV.MDB). D3.4 Enhanced Prediction Runs in GAP Using the OPENSERVER for GAP, the prediction can be run one step at a time. This means that values can be changed during the prediction. For example, you could write a VBA macro to change the PI when an acid job has been performed on a well. D3.5 Running PETEX programs with other

engineering software applications The OPENSERVER can be used to run the PETEX programs in conjunction with other software applications and exchange data between them. For example, a visual basic program or batch file could be used to successively: Run a process simulator to calculate a feed separator pressure

Set the separator pressure in GAP

Optimize the production system in GAP

Pass the GAP rates onto the process simulator

Run the process simulator and so on…



D4 Support The main strength of the OPENSERVER is that users are now free to develop their own applications which utilise the public functions within PETEX products. However this does mean that a user of the OPENSERVER will require more computing knowledge than a user of the standard PETEX programs. This is particularly the case where a user writes a client application in VBA or Visual Basic. The user is expected to have (or be trained in) the requisite computing skills to write these client applications. Petroleum Experts will not be able to undertake to train users in these computing skills. The boundary of the PETEX products and the users applications needs to be defined with respect to support provided by Petroleum Experts of the OPENSERVER feature. Firstly, as with normal support, a maintainance agreement between the user and Petroleum Experts must be in place. Unfortunately, Petroleum Experts will not be able to undertake development of VBA macros, batch files or other OPENSERVER clients for a particular user. The strength of the feature is to allow the user to implement these client applications without any further input by Petroleum Experts. Similarly Petroleum Experts will be unable to assist in fixing bugs in users VBA macros, batch files or any other OPENSERVER client. Petroleum Experts will undertake to support any user who can demonstrate (through a simple fragment of a batch file or VBA macro etc) that a public function call to a PETEX product fails to work correctly.

PVTP User Guide


D5 Using the OPENSERVER This section describes in detail how to access the public function in PETEX programs. The first section describes how we identify each data item in the PETEX programs using a variable text string. The second section describes how to call the public functions using Automation. We first describe the framework needed to use the OPENSERVER, then each function is described in detail. The third section describes how to call the public functions using a batch file system. We describe the framework and then describe each function in detail. This section does not deal with specific issues relating to particular products e.g. GAP or PVTP. To use the public function for a particular PETEX program you will need the program installed on your hard disk and valid security authentication e.g. security key or hardlock. When the public functions are being called (either using Automation or a batch file), the appropriate PETEX product must be running. However, it does not need to be visible on the screen (i.e. it can be minimized). D5.1 Variable Text Strings Variable text strings describe each data item in the PETEX programs. It is a string of characters which is broken into a number of subnames separated by full stops. As one moves from left to right along the string the definition of the variable becomes more detailed. The variable text string of any data item in PVTP always begins with the subname “PVT”. Similarly, any data item from GAP , PROSPER or MBAL will begin with the subname “GAP” , “PROSPER” or “MBAL” respectively. The rest of the string depends on the section of the program. There may be several subnames if the data item is part of a complex hierarchy. For example, for the start time in the material balance prediction we may have “MBAL.MB.PRED.STARTTIME". For this text string: MBAL – From the MBAL program MB – In the material balance tool PRED – In the prediction section STARTTIME – Start time For collections/lists the rules become more complex. Take the example of the list of tanks in MBAL. The particular tank pressure can be specified in three ways:- "MBAL.MB.TANK.PRESSURE" - In this case we do not specify any particular tank. It will use the currently selected tank in the collection. This should only be used if there is known to be only one tank in the collection. "MBAL.MB.TANK[0].PRESSURE" - This will use the 0th tank in the list - this is a zero based index. This is most likely to be used if we are iterating through the list of tanks.



"MBAL.MB.TANK[{S-Tank}].PRESSURE" - This specifies the tank by the name. Note that we enclose the name by curly brackets to avoid any confusion with names made up with digits only. We can use GetValue to retrieve the number of objects in a collection. In this case we would send the variable text string "MBAL.MB.TANK.COUNT". All variable text strings are case insensitive i.e. it does not matter if you use lower or upper case characters. For specific details of the variable text strings for each PETEX program, refer to the program specific sections below. D5.2 Automation This section describes how to access the public functions using Automation. This is a Microsoft Windows standard (formally known as OLE Automation). This method requires software which can act as an Automation client to call the public functions. Probably the most commonly used example of such an Automation client that is used in the engineering industry is the VBA macro language within Excel. We will therefore demonstrate how the public functions are called by such macros – the same rules should extend to other Automation clients. Rather than describing the functions in isolation, an example of an Excel VBA macro is presented that uses all the available public functions. Each function within this example can then be described.

PVTP User Guide


D5.2.1 Example Macro This example performs a simple set of operations in the MBAL program. These include:

Open the OIL.MBI file Change the original oil in place to a new value Run a prediction Get the first oil rate and display it in the spreadsheet.

This macro is available in the installed MBAL examples, OPENSERV.XLS. The macro is split into a number of subroutines and functions. The main subroutine is called DoAll(). There are five other subroutines and functions which allow calls to be made to the PETEX public functions.

Option Explicit Dim Server As Object Dim AppName As String Sub DoAll() Set Server = CreateObject("PX32.OPENSERVER.1") AppName = "MBAL" DoCmd "MBAL.OPENFILE=C:\PETEX\SAMPLES\OIL.MBI" DoSet "MBAL.MB.TANK.OOIP", "250.0" DoSlowCmd "MBAL.MB.RUNPREDICTION" Range("C11") = DoGet("MBAL.MB.TRES[2][0][0].OILRATE") Set Server = Nothing

MsgBox "Macro completed" End Sub Sub DoCmd(Cmd)

Dim lErr As Long lErr = Server.DoCommand(Cmd) If lErr > 0 Then MsgBox Server.GetErrorDescription(lErr) Set Server = Nothing End End If End Sub Sub DoSet(Sv, Val)

Dim lErr As Long lErr = Server.SetValue(Sv, Val) lErr = Server.GetLastError(AppName) If lErr > 0 Then MsgBox Server.GetErrorDescription(lErr) Set Server = Nothing End End If End Sub Function DoGet(Gv As String) As String

Dim lErr As Long DoGet = Server.GetValue(Gv) lErr = Server.GetLastError(AppName) If lErr > 0 Then MsgBox Server. GetErrorDescription(AppName) Set Server = Nothing End End If End Function Sub DoSlowCmd(Cmd) Dim StartTime As Single Dim EndTime As Single Dim CurrentTime As Single Dim lErr As Long Dim bLoop As Boolean lErr = Server.DoCommandAsync(Cmd) If lErr > 0 Then



MsgBox Server.GetErrorDescription(lErr) Set Server = Nothing End End If While Server.IsBusy(AppName) > 0 StartTime = Timer EndTime = StartTime + 2 Do CurrentTime = Timer DoEvents bLoop = True Rem Check first for the case where we have gone over midnight Rem and the number of seconds will go back to zero If CurrentTime < StartTime Then bLoop = False Rem Now check for the 2 second pause finishing ElseIf CurrentTime > EndTime Then bLoop = False End If Loop While bLoop Wend lErr = Server.GetLastError(AppName) If lErr > 0 Then MsgBox Server.GetErrorDescription(lErr) Set Server = Nothing End End If End Sub Function DoGAPFunc(Gv As String) As String AppName = “GAP” DoSlowCmd Gv DoGAPFunc = DoGet("GAP.LASTCMDRET") End Function

D5.2.2 Framework There are only a few lines that need to be in an Excel macro to use the OPENSERVER Firstly before using any of the public functions, you must declare an object through which you will communicate with the PETEX programs:

Dim Server As Object Next, you must connect the object to the OPENSERVER using the line:

Set Server = CreateObject("PX32.OPENSERVER.1") Once the server is connected, you can use the Server object to call any number of functions from any or all of the PETEX programs, e.g.:

Server.DoCommand(Command1) Server.DoCommand(Command2) Server.GetValue(Var1)

Once you have finished calling the public functions in your macro, you may close the server object using the line:

Set Server = Nothing These can be seen in the DoAll() subroutine above.

PVTP User Guide


D5.2.3 DoCommand This function is used to perform calculations (and other functions such as file opening and saving) in the PETEX programs. Only a subset of the calculations available using the user interface are available. The calculations that are not supported are often those that require some graphical interaction e.g. graphical history matching in MBAL. In the above example, the DoCommand function is handled by the macro subroutine DoCmd(). It is used in the DoAll() subroutine to open the OIL.MBI file. The command to be performed is determined by the input text string. In our example this is “MBAL.OPENFILE=C:\PETEX\SAMPLES\OIL.MBI” which tells MBAL to open the specified file name. Check the following product specific sections describing each PETEX program for a list of possible commands. The return value of DoCommand indicates any error status for the function call. If the return value is zero then the command completed with no error. If the return value is a positive number, an error occurred in the command and the number indicates the nature of the error. The DoCmd() macro subroutine checks the return value of DoCommand() and if a problem is detected, it calls another PETEX public function called GetErrorDescription(). This function returns a description of the error which can then be displayed to the user of the macro. Unless you have good reason to do otherwise, it is recommended that you re-use the DoCmd() macro subroutine in the example macro for all your own applications as it already has error handling built in. D5.2.4 SetValue This function is used to set the value of a data item. It should be possible to change most of the values that can normally be accessed via the user interface. Each variable is identified by the unique text string. In the above example, the SetValue function is handled by the macro subroutine DoSet(). It is used in the DoAll() subroutine to change the value of the initial oil in place to 250.0. The variable to be changed is determined by the first input text string. The new value for the variable is passed in the second input text string. This function expects the value to be in the units currently displayed in the user interface. It is the responsibility of the user writing the macro to ensure that the second text string contains a valid number if the data item is numerical. Unlike the DoCommand public function, the SetValue function does not return an error number. As can be seen in the example macro subroutine DoSet(), you must call another public function, GetLastError(), to check if any error occurred. This will return zero if the last public function call was successful or an error number if not. Unless you have good reason to do otherwise, it is recommended that you re-use the DoSet() macro subroutine shown in the example macro for all your own applications as it already has error handling built in.



D5.2.5 DoCommandAsync This function is a variation of the DoCommand function. It is nearly always used in conjunction with the IsBusy() function. When a VBA macro is run, it executes and completes each line before moving onto the next line. So when you call the DoCommand function for a long prediction, it may take several minutes (or even hours) before the VBA can move onto the next line in the macro. Unfortunately, VBA was designed for use with simple functions that take only a few seconds. If a function is called that takes more than one minute to complete, a timeout error in Excel may occur depending on operating system, Excel version, setup etc.. The DoCommandAsync function allows you to call functions that take a long time to complete without any risk of timeouts in your VBA. When you call DoCommandAsync, the OPENSERVER starts the calculation in the PETEX program but lets the VBA carry immediatley on to the next line in the macro. This avoids the timeout error in Excel. Unfortunately it introduces another problem. What if the next line in the macro was a call to the GetValue function to get the results of the calculation? The macro is likely to try to get the calculated value before the calculation is finished! So the VBA still needs some way of knowing when the calculation has finished. Therefore it is usually necessary to append some VBA code after a call to DoCommandAsync which loops until the calculation is finished. The inserted code uses another function called IsBusy() to check if the calculation is finished. This VBA code to do this is in the macro subroutine DoSlowCmd() in the example macro. The code loops round until the IsBusy function returns a value greater than zero. The only input argument is the name of the PETEX program in which the calculation was called. Within the loop the code will wait 2 seconds before looping again. It also calls the VBA function, DoEvents, which will allow other windows program to work whilst the VBA is waiting for the calculation to finish. Unless you have good reason to do otherwise, it is strongly recommended that you re-use the DoSlowCmd() macro subroutine shown in the example macro for all your own applications as it already has error handling built in as well as the code to wait for the function to finish. D5.2.6 GetValue This function is used to get the value of a data item. It should be possible to query most of the values that can normally be accessed via the user interface. Each variable is identified by a unique text string. In the above example, the GetValue function is handled by the macro function DoGet(). It is used in the DoAll() subroutine to get the value of the first oil rate in the prediction tank results. The variable to be retrieved is determined by the input text string. The return value of the function call is another text string containing the value of the data item. If the value is numerical data, the return text string will contain the formatted number – this avoids having different functions for different data types. The value will be returned in the units currently displayed in the user interface.

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As with the SetValue function, you must use the GetLastError function to check for errors in the SetValue function. Note that in the macro subroutine DoGet(), we use a different function to get the actual error message – GetLastErrorMessage(). This function returns the error message corresponding to the last public function call for the application specified by the input argument. If the last public function call was successful, it will return a blank error message. Unless you have good reason to do otherwise, it is recommended that you re-use the DoGet() macro function shown in the example macro for all your own applications as it already has error handling built in.



D5.3 Batch File This section describes how to access the public functions using a batch file. Each command is typed into an ASCII file. A program is supplied by Petroleum Experts which reads this ASCII file, calls the public functions in the PETEX programs and writes the output to another ASCII file. D5.3.1 Running a Batch File The first step to calling the public functions from the batch file is to create the batch file itself. This is a simple ASCII file which can be created using NOTEPAD.EXE. The only point to note is that when you save the batch file it should have the file extension PXB e.g. TEST.PXB. Each public function to be called should be listed on a separate line. Comment lines can be entered by starting the line with a # character e.g. # This is my first batch file # 11th January 1999 The details of how to list the public functions is shown in the following sections. Once the batch file has been created and the functions listed in the file, we can run the batch file. First run the latest version of the PETEX program you are going to use e.g. MBAL and GAP. Next copy the file PXBATCH.EXE into the same directory as your PXB batch file. This file can be found in your latest installation of the PETEX CD – probably C:\PETEX. Finally run the PXBATCH program with the PXB file name as an argument. For example, if the batch file is called TEST.PXB, run: PXBATCH –b TEST PXBATCH will call each public function in turn. Two files will be created by PXBATCH. The first is called PXBATCH.LOG. This file will contain any error messages from the batch run so it is important to examine the file after every batch run to check for errors. The second file will have the same file stem as the batch file but will have the extension PXR. In the above case, the second output file will be called TEST.PXR. This file will contain any output from the public functions. An example batch will be presented which shows calls to all the public functions in the PETEX products. Then each function used in the example batch file will be described in turn. The example batch file is as follows (this file is available in the installed MBAL examples, MBALTEST.PXB).:-

# Example batch file PRINT Example batch file output PRINT docommand MBAL.OpenFile("C:\PETEX\SAMPLES\OIL.MBI") setvalue MBAL.MB.TANK.OOIP 250.0 docommand MBAL.MB.RUNPREDICTION getvalprint MBAL.MB.TANK.OOIP PRINT "First oil rate =" PRINTTAB PRINTTAB getvalue MBAL.MB.TRES[2][0][0].OILRATE PRINT " bbls/day" PRINT

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PRINT End of example batch file output

The output PXR file from the above batch file is as follows: 250 ! MBAL.MB.TANK.OOIP First oil rate = 16516.8 bbls/day End of example batch file output

D5.3.2 Formatting Commands There are two commands, PRINT and PRINTTAB that can be used to format and write text to the output PXR file. The PRINT statement can be used in two ways. If you append some text to the PRINT statement, the text will be printed out to the PXR file. You may enclose the text in quotations if desired. If you use the PRINT command without any text, it will move the output onto the next line in the PXR file. For example, consider the last three lines of the example batch file. The first of these PRINT statements prints the text “ bbls/day”. The second PRINT statement moves the next output onto the next line. The third PRINT statement displays the text “End of example batch file output” on the next line of the PXR file. Note that if the second PRINT statement was not included, the output PXR file would look like:

…..bbls/dayEnd of example batch file output

The second formatting command is PRINTTAB. This command simply writes a tab character to the PXR file. D5.3.3 DoCommand This function is used to perform calculations (and other functions such as file opening and saving) in the PETEX programs. Only a subset of the commands available using the user interface are available. The commands that are not supported are those that require some graphical interaction e.g. graphical history matching in MBAL. In the example, DoCommand is used twice. The first time it is used to open a data file. The second time it is used for running a prediction. The text string after the DoCommand statement describes the command to be performed. The text string always starts with the name of the program in which the calculation is to be done. The rest of the text string describes the command – check the following sections describing each PETEX program for a list of possible calculations. There is no output to the PXR file for this command. If there is any error, a message will be written to PXBATCH.LOG. Note that the abbreviation dc can be used in the batch file instead of DoCommand. D5.3.4 SetValue This function is used to set the value of a data item. It should be possible to change most of the values that can normally be accessed via the user interface. In the example we use SetValue once to change the original oil in place to 250.0. The first text string after SetValue defines the variable to be changed. The second



text string defines the new value of the variable. This function expects the value to be in the units currently displayed in the user interface. There is no output to the PXR file for this command. If there is any error, a message will be written to PXBATCH.LOG. Note that the abbreviation sv can be used in the batch file instead of SetValue. D5.3.5 GetValue and GetValPrint These two functions are both used to get the value of a data item and print it to the PXR output file. The only difference between the two functions is the format of the output to the PXR file. GetValPrint is used once in the example batch file to get the value of the original oil in place – this is to verify that the preceding SetValue worked correctly. The text string after GetValPrint defines the variable that you wish to write to the output PXR file. If the function works correctly, the variable is written to the PXR file followed by the variable text string, separated by an exclamation mark. It also moves the output onto the next line so any further Print functions will start on the next line. This format can be seen in the example PXR file above. GetValue is also used once in the example batch file to output the first oil rate in the prediction tank results. The function is called as for GetValPrint. The only difference is that this function simply writes the value of the variable to the output PXR file without any formatting. This means that you will need to use other Print commands to format the output – as shown in the example batch file. Note that the abbreviation gvp can be used in the batch file instead of GetValPrint. The abbreviation gv can be used instead of GetValue.

PVTP User Guide


D6 PVTP and the OPENSERVER D6.1 OverView OPEN SERVER is designed to provide an Open Architecture for Petroleum Experts products. This allows the programs to be accessed and driven by other programs such as Excel.For a fuller description of the OPENSERVER, the user should consult the manual on this subject which is distributed with the suite of programs. In common with all the programs, the labels used within the OPENSERVER can be visualised by pressing Ctrl while doing a mouse right click when over a specific dialog item. A comprehensive series of Excel spreadsheets are distributed with PVTP. All major labels, methods and calculations are illustrated within these files. The main areas that can be accessed via the PVTP OPENSERVER are:

BLACKOIL OPTIONS STREAMBASE[stream no. or stream name] STREAMRUN[stream no. or stream name] CALCUL[stream no. or stream name]

Note At present, no access is given to matching within the blackoil or equation of state models.



D6.2 File and Streams PVTP has a Multiple Document Interface(MDI) . This means the program can load more than one *.pvi file. The files are manipulated using the following commands:

OPENFILE Opens a pvi file SAVEFILE Saves the active file with the given file name CLOSEFILE Closes the active file without saving it SHUTDOWN Closes all files without saving them SETACTIVEFILE Sets named file as the active document UPDATEDISPLAY Instucts program to update the main screen with the

latest active file data

The file commands are demonstrated in the OPENPVT.XLS sample Excel file. Each file can contain multiple streams. Each stream contains Base, Runtime and Calculation data. Individual streams can be accessed by way of a zero-based index or the stream name.

A typical string to get a piece of stream data would be:

PVT.STREAMBASE[{WellStream}].COMPOSITION[1]

This accesses the composition of the second component within the stream called WellStream. Details of stream contents are described in Sections 8.4 and 8.5.

The stream commands are demonstrated in the OPENPVT.XLS sample Excel file.

Streams can be manipulated using the following:

CREATE_EMPTY_STREAM Adds an empty stream to the active file SET_ACTIVE_STREAM Sets the active stream within the active

file COPY_STREAM Copies an identified stream within the

active file COPYSTREAMBASE_TO_STREAMRUN Copies BASE data to RUNTIME for the

identified stream COPYSTREAMRUN_TO_STREAMBASE Copies RUNTIME data to BASE for the

identified stream

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D6.3 BLACKOIL This section deals with access to the input data and calculations within the Blackoil model of the PVTP program. Use of the model and data is demonstrated within the OPEN_BLACKOIL_CALC.XLS sample Excel file. The setting of the file to a blackoil model is done within the options section with the DoSet command. "PVT.OPTIONS.METHOD” with value BLACKOIL" The type of model is set by “PVT.OPTIONS.FLUIDTYPE” to “OIL”,”GAS” or “CONDENSATE” There is only one set of blackoil data per file so no stream indication is required. To obtain a piece of blackoil data the command string would be: "PVT.BLACKOIL.SEPPRESS".

CORRPB Correlation for PB,Rs,Bo CORRUO Correlation for Oil Viscosity CORRUG Correlation for Gas Viscosity SOLGOR Solution GOR OILGRAV Oil Gravity GASGRAV Gas Gravity SEPPRESS Separator Pressure SEPTEMP Separator Temperature SEPGOR Separator GOR SEPGASGRAV Separator Gas Gravity TANKGOR Tank GOR TANKGASGRAV Tank Gas Gravity CGR Condensate to Gas Ratio H2S H2S Concentration CO2 CO2 Concentration N2 N2 Concentration DEWPOINT Condensate Dewpoint RESTEMP Reservoir Temperature RESPRESS Reservoir Pressure WATER_SALINITY Water Salinity PVT_MATCHED Flag to indicate that PVT is matched



D6.4 OPTIONS This section deals with access to common options within the active PVTP file. The options deal with many aspects of how and where models are used, which calculations are carried out etc.

The Options sheet within the the OPENPVT.XLS sample Excel file, gives an indication of how these data points can be accessed. A typical DoSet command would be " PVT.OPTIONS.VISCMETHOD” with value “LOHRENZ” sets the model for EoS calculations to Lohrenz Bray Clark.

The options available include:

METHOD Defines the model being used i.e. BLACKOIL or EOS FLUIDTYPE Defines the blackoil model to be used i.e OIL,GAS or

CONDENSATE SEPARATORTYPE Defines the number of separators within a blackoil

model i.e. SINGLE ot TWO EOSTYPE Defines the equation to be used for the EoS model

i.e. PENGROB or SRK COMPANY Gives access to the Company string within the

Options Dialog FIELD Gives access to the Field string within the Options

Dialog LOCATION Gives access to the Location string within the Options

Dialog PLATFROM Gives access to the Platform string within the Options

Dialog ANALYST Gives access to the Analyst string within the Options

Dialog COMMENT Gives access to the Comment string within the

Options Dialog CALC_TYPE Sets the active calculation. See Calculations Section

8.7 for more details CALC_TYPE Sets the flash type for mixtures with water or solids to

MULTIPHASE or TWOPHASE VISCMETHOD Sets the viscosity model for EoS calculations USE_VOLSHIFT Switches volume shift on and off during EoS

calculations CALC_PSAT_IN_CMPGRAD Flag to calculate Saturation Pressure during

compositional gradient calculation CALC_PSAT_IN_CCE Flag to calculate Saturation Pressure during CCE

calculation CALC_THERMALCOND_IN_CCE

Flag to calculate Thermal Conductivity during CCE calculation

USE_ADV_PHASE_DETECTION

Preferences|Calc Tolerences: Use advanced phase detection flag

SHOW_CALCS Preferences|Calc Tolerences: Show calculated values during calculation flag

OPTIMISE_REGRESSION Preferences|Calc Tolerences: Optimise calculations during regression flag

OPTIMISE_CVD_REGRESSION

Preferences|Calc Tolerences: Optimise CVD calculation during regression flag

REGRESS_MAXSTEPS Preferences|Calc Tolerences: Maximum number of iterations during regression

PHASE_CALC_MAXITER Preferences|Calc Tolerences: Maximum number of iterations during phase check

PHASE_CALC_MINPRESS Preferences|Calc Tolerences: minimum pressure during phase check

PHASE_CALC_VAPTEST Preferences|Calc Tolerences: vapour fraction used as

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test in phase check OVERRIDE_PHASE_CALC Preferences|Calc Tolerences: override phase check

and force phase FIXED_PHASE Preferences|Calc Tolerences: forced phase after

phase check override FORTLIB_ITERATIONS Preferences|Calc Tolerences: Fortran library

maximum iterations FORTLIB_PRECISION Preferences|Calc Tolerences: Fortran library

calculation precision SHOWPLOT_POINTS Preferences|Calc Tolerences: Show points on plots CALC_GOR_CORRECTED_WITH_SEPS

Flag to correct FVF and GOR within CCE, CVD etc. through a separator train

REGR_GOR_CORRECTED_WITH_SEPS

Flag to correct FVF and GOR through a separator train during regression

TARGET_GOR_CORRECTED_WITH_SEPS

Flag to flash through a separator train to get gas and oil used in Target GOR calc.

USE_INDIVIDUAL_SEP_CORRECTION

Flag to use individual stream values for separator correction.

VOLSHIFT_D Volume Shift D parameter VOLSHIFT_E Volume Shift E parameter ECLIPSE_OILTYPE Eclipse Blackoil Export:Option for oil ECLIPSE_GASTYPE Eclipse Blackoil Export:Option for gas ECLIPSE_WATERTYPE Eclipse Blackoil Export:Option for water WAXTEMP_NUMSTEPS Wax Appearance Temperature Calc.:Max number of

steps WAXTEMP_MINTEMP Wax Appearance Temperature Calc.:minimum

temperature WAXTEMP_MAXTEMP Wax Appearance Temperature Calc.:maximum

temperature WAXTEMP_TESTSOLIDS Wax Appearance Temperature Calc.:solids value

used as test WAX_MODEL Selects model used in wax calculations HYDRATE_METHOD Selects method used in hydrate calculations HYDRATE_INHIBITOR Selects inhibitor used in hydrate calculations HYDRATE_USE_INHIBITOR Flag to say whether inhibitor is used in hydrate

calculations HYDRATE_USE_INHIBITOR Flag to say whether hydrate II is calculated in

hydrate calculations SLIMTUBE_TEST_RECOVERY

Slimtube calculation test value for recovery

SLIMTUBE_TEST_POREVOL

Slimtube calculation test value for pore volume

PHASE_ENV_THETA_VALUES

Phase Envelope Calculation: vapour fractions that are to be calcualted

CREATE_MAX_ITERATIONS

Create Streams to target GOR and PSAT:maximum number of iterations

CREATE_GOR_END_TEST Create Streams to target GOR:test of target value being found

CREATE_PSAT_END_TEST Create Streams to target PSAT:test of target value being found

CREATE_PSAT_PHASE Create Streams to target PSAT:phase to be produced D6.5 STREAMBASE[stream no. or stream name] This structure is the main depository for defining a stream. It contains component definitions, properties, reference data etc. Unlike the STREAMRUN version below, this data is saved with the file. The command COPYSTREAMRUN_TO_STREAMBASE will put runtime data into the base structure for saving. See the distributed Excel File OPENPVT.XLS for the main set of variables and calls which manipulate streams etc.

A typical string to get a piece of stream data would be:



PVT.STREAMBASE[{WellStream}].CRITTEMP[8] This accesses the critical temperature of the ninth component within the stream called WellStream.

The stream variables available include:

STREAMNAME Accesses the stream name of the indicated

stream STREAMCOMMENT Accesses the stream comment of the

indicated stream NUMCOMPONENTS Accesses the stream number of

components NUMPSEUDOS Accesses the stream number of pseudo

components RESTEMP Accesses the stream reservoir temperature REFPRESS Accesses the stream refererence pressure REFDEPTH Accesses the stream refererence depth STANDPRESS Accesses the stream standard pressure STANDTEMP Accesses the stream standard temperature WATERSALINITY Accesses the stream water salinity value COMPONENT[x] Accesses name of component x (zero

based index) COMPONENT_LONG[x] Accesses description of component x (zero

based index) COMPONENT_TYPE[x] Accesses type of component x (zero based

index) 0 – no type 1- HC 2 – NON-HC 3 – CUSTOM 4- PSEUDO

COMPONENT_INDEX[x] Accesses where component x (zero based index) is within database

COMPOSITION[x] Accesses composition of component x (zero based index)

CRITTEMP[x] Accesses critical temperature of component x (zero based index)

CRITPRESS[x] Accesses critical pressure of component x (zero based index)

CRITPVOL[x] Accesses critical volume of component x (zero based index)

ACCENFACT[x] Accesses accentric factor of component x (zero based index)

OMEGAA[x] Accesses OmegaA value of component x (zero based index)

OMEGAB[x] Accesses OmegaB value of component x (zero based index)

MOLEWT[x] Accesses molecular weight value of component x (zero based index)

PARACHOR[x] Accesses parachor value of component x (zero based index)

BOILPT[x] Accesses boiling point of component x (zero based index)

SPECGRAV[x] Accesses specific gravity of component x (zero based index)

RHOAPP[x] Accesses apparent density of component x (zero based index)

VOLSHIFTC[x] Accesses volume shift C parameter of component x (zero based index)

VOLSHIFTS[x] Accesses volume shift S parameter of component x (zero based index)

ZRACK[x] Accesses Z Rackett parameter of component x (zero based index)

ZCRIT[x] Accesses critical Z factor of component x (zero based index)

MELTPT[x] Accesses melting point of component x (zero based index)

HEATFUSION[x] Accesses heat of fusion of component x

PVTP User Guide


D6.6 STREAMRUN[stream no. or stream name] This structure is the temporary description of a stream which is used in calculations. It is similar to STREAMBASE and contains component definitions, properties, reference data etc. Unlike the STREAMBASE version above, this data is not saved with the file. The command COPYSTREAMBASE_TO_STREAMRUN will put base data into the runtime structure prior to calculations. See the distributed Excel File OPENPVT.XLS for more details and examples. Of particular interest is the example of the Flash calculation within this file , as it demonstates how the runtime input data and the runtime calculation results can be utilised.

A typical string to get a piece of runtime data would be: PVT.STREAMRUN[{WellStream}].CRITPRESS[0]

This accesses the critical pressure of the first component within the stream called WellStream.

The stream runtime variables available include:

NUMCOMPONENTS Accesses the runtime number of components NUMPSEUDOS Accesses the runtime number of pseudo

components RESTEMP Accesses the runtime reservoir temperature REFPRESS Accesses the runtime refererence pressure REFDEPTH Accesses the runtime refererence depth TEMPERATURE Accesses the calculation temperature PRESSURE Accesses the calculation pressure STANDTEMP Accesses the runtime standard temperature WATERSALINITY Accesses the runtime water salinity value COMPONENT[x] Accesses name of component x (zero based

index) COMPONENT_LONG[x] Accesses description of component x (zero

based index) COMPONENT_TYPE[x] Accesses type of component x (zero based

index) 0 – no type 1- HC 2 – NON-HC 3 – CUSTOM 4- PSEUDO

COMPONENT_INDEX[x] Accesses where component x (zero based index) is within database

COMPOSITION[x] Accesses composition of component x (zero based index)

CRITTEMP[x] Accesses critical temperature of component x (zero based index)

CRITPRESS[x] Accesses critical pressure of component x (zero based index)

CRITPVOL[x] Accesses critical volume of component x (zero based index)

ACCENFACT[x] Accesses accentric factor of component x (zero based index)

OMEGAA[x] Accesses OmegaA value of component x (zero based index)

OMEGAB[x] Accesses OmegaB value of component x (zero based index)

MOLEWT[x] Accesses molecular weight value of component x (zero based index)

PARACHOR[x] Accesses parachor value of component x (zero based index)

BOILPT[x] Accesses boiling point of component x (zero based index)

SPECGRAV[x] Accesses specific gravity of component x (zero based index)

RHOAPP[x] Accesses apparent density of component x (zero based index)

PVTP User Guide


VOLSHIFTC[x] Accesses volume shift C parameter of component x (zero based index)

VOLSHIFTS[x] Accesses volume shift S parameter of component x (zero based index)

ZRACK[x] Accesses Z Rackett parameter of component x (zero based index)

ZCRIT[x] Accesses critical Z factor of component x (zero based index)

MELTPT[x] Accesses melting point of component x (zero based index)

HEATFUSION[x] Accesses heat of fusion of component x (zero based index)

SOLPAR[x] Accesses solubility parameter of component x (zero based index)

SOLPARSOLID[x] Accesses solid solubility parameter of component x (zero based index)

RESULT_KVALUES [x] Last Calc Results: K Value of component x (zero based index)

LIQUID_COMPOSITION [phase][x]

Last Calc Results: liquid composition of component x in liquid phase ph (zero based indices)

VAPOUR_COMPOSITION [0][x] Last Calc Results: vapour composition of component x in vapour phase 0 (zero based indices)

SOLID_COMPOSITION [0][x] Last Calc Results: lsolid composition of component x in vapour phase 0 (zero based indices)

DENSITY [ph] Last Calc Results: density of phase ph 0 – vapour , 1 - liquid

ZFACTOR [ph] Last Calc Results: z factor of phase ph 0 – vapour , 1 - liquid

VISCOSITY [ph] Last Calc Results: viscosity of phase ph 0 – vapour , 1 - liquid

SPECIFIC_ENTHALPY [ph] Last Calc Results: enthalpy of phase ph 0 – vapour , 1 - liquid

SPECIFIC_ENTROPY [ph] Last Calc Results: entropy of phase ph 0 – vapour , 1 - liquid

CP [ph] Last Calc Results: specific heat Cp of phase ph 0 – vapour , 1 - liquid

CV [ph] Last Calc Results: specific heat Cv of phase ph 0 – vapour , 1 - liquid

SPEEDOFSOUND [ph] Last Calc Results: speed of sound of phase ph 0 – vapour , 1 - liquid

JTHOMSONCOEFF [ph] Last Calc Results: Joule-Thomson coeff.of phase ph 0 – vapour , 1 - liquid

THERMALCOND [ph] Last Calc Results: Thermal Cond..of phase ph 0 – vapour , 1 - liquid

IFT Last Calc Results: Interfacial tension of mixture VAP_FRACTION Last Calc Results: Vapour fraction calculated SOLID_FRACTION Last Calc Results: Solid fraction calculated WATER_FRACTION Last Calc Results: Water fraction calculated NON_WATER_FRACTION Last Calc Results: Hydrocarbon fraction

calculated NUM_PHASES Last Calc Results: Multiphase flash number of

phases detected NUM_LIQUID_PHASES Last Calc Results: Multiphase flash number of

phases detected PROFILEOILFRACTION [n] Profile Calc: dead oil fraction n PROFILESATPRESS[n] Profile Calc: Saturation Pressure for dead oil

fraction n PROFILEPHASE [n] Profile Calc: phase detected for dead oil fraction

n PROFILE_BLEND_FRACTION [n] Profile Calc: fraction of stream 1 added to blend PROFILE_BLEND_GOR [n] Profile Calc: GOR calculated for blend fraction

n



D6.7 CALCUL[stream no. or stream name] This structure controls the calculations. It contains the vaules of calculation ranges, intermediate values results and analysis. The distributed spreadsheets illustrate the following calculations:

OPENPVT.XLS the FLASH calculation. This is a core calculation which has been specifically packaged up for the OPENSERVER.

OPEN_CRITPOINT_PHASE_ENV_CALC.XLS Mixture Critical Point and Phase Envelope

OPEN_CCE_PSAT_CALC.XLS Single point and ranged saturation pressure plus constant composition expansion.

OPEN_CVD_DEPL_CALC.XLS Constant volume depletion and depletion study.

OPEN_DIFF_COMPOS_CALC.XLS differential Liberation and Composite Differential

OPEN_SEP_CALC.XLS small and full separator calculations

OPEN_COMPGRAD_SWELL_CALC.XLS Compositional gradient and Swelling Test.

OPEN_SLIMTUBE_CALC.XLS Slim Tube Calculation

OPEN_HYDRATE_CALC.XLS Hydrate formation pressure OPEN_WAX_CALC.XLS Wax amount and wax appearance temperature

OPEN_CALCS_WITH_WATER.XLS Multiphase CCE and separator calculation with water present

OPEN_BLACKOIL_CALC.XLS CCE calculation as used in the blackoil export table.

OPEN_UTILITIES.XLS Utility calculations i.e. isenthalpic flash,water saturation, create stream to target GOR,create stream to a target PSAT. The procedure used to initiate calculations and retrieve results is outlined in section 8.8

A typical string to get a piece of runtime data would be:

PVT.CALCUL[{WellStream}]. CALC_USER_CCE_TEMPS [4] This accesses the fifth user-defined temperature input value for the CCE calculation within the stream called WellStream. The stream runtime variables available include:

CALC_MODE Flag to set calculation mode to automatic or user-defined (for calcs without individual flag see rest of table)

CALC_CCE_MODE Flag to set calculation mode to automatic or user-defined for CCE

CALC_GRAD_MODE Flag to set calculation mode to automatic or user-defined for compositional gradient

CALC_WAXTEMP_MODE Flag to set calculation mode to automatic or user-defined for wax appearance temperature

PVTP User Guide


CALC_WAXTEMP_MODE Flag to set calculation mode to automatic or user-defined for wax appearance temperature

CALC_ECLIPSE_MODE Flag to set calculation mode to automatic or user-defined for eclipse export

UTILS_ENTHALPY_BALANCE_MODE Flag to set calculation mode to automatic or user-defined for utilities enthalpy balance calculation

EXP_SAT_UNSAT_MODE Flag to set calculation mode to automatic or user-defined for variable bubble point export

SLIMTUBE_MODE Flag to set calculation mode to automatic or user-defined for slim tube calculation

UTILS_WATERSATN_MODE Flag to set calculation mode to automatic or user-defined for utilities water saturation calculation

CALC_HYDRATE_MODE Flag to set calculation mode to automatic or user-defined for hydrate calculation

CALC_FIRST_STREAM First stream index – SWELL etc.calculation CALC_SECOND_STREAM Second stream index – SWELL etc.calculation CALC_NUM_RESULTS Number of lines of results calculated CALC_NUM_CURVES Number of curves calculated for phase

envelope CALC_MIN_TEMP Calculation minimum temperature CALC_MAX_TEMP Calculation maximum temperature CALC_MIN_PRESS Calculation minimum pressure CALC_MAX_PRESS Calculation maximum pressure CALC_USER_TEMPERATURES[n] Calculation user-defined temperatures CALC_USER_PRESSURES[n] Calculation user-defined pressures CALC_NUM_DEPTHABOVEVALUES Gradient :number of depths above reference CALC_MAX_DEPTHABOVE Gradient :maximum of depths above reference CALC_NUM_DEPTHBELOWVALUES Gradient :number of depths below reference CALC_MAX_DEPTHBELOW Gradient :maximum of depths below reference CALC_CMPGRAD_DEPTHABOVE Gradient :user-defined depths above reference CALC_CMPGRAD_DEPTHBELOW Gradient :user-defined depths below reference CALC_TEMP_GRADIENT Gradient :temperature gradient value CALC_USE_RELATIVE_DEPTHS Gradient :temperature gradient value CALC_SEP_PRESSURES[n] Separator Calculation : stage pressures CALC_SEP_TEMPERATURES Separator Calculation : stage temperatures CALC_PSAT_MIN_TEMP PSAT Calculation auto minimum temperature CALC_PSAT_MAX_TEMP PSAT Calculation auto maximum temperature CALC_PSAT_NO_VALUES PSAT Calculation auto no of values CALC_USER_CCE_TEMPS[n] CCE Calculation : user-defined temperatures CALC_USER_CCE_PRESSURES[n] CCE Calculation : user-defined pressures CALC_CCE_NO_TEMP_VALUES CCE Calculation : auto number of temperatures CALC_CCE_NO_PRESS_VALUES CCE Calculation : auto number of pressures CALC_CCE_MAX_TEMP

CCE Calculation : auto maximum temperature

CALC_CCE_MIN_TEMP

CCE Calculation : auto minmum temperature

CALC_CCE_MAX_PRESS

CCE Calculation : auto maximum pressure

CALC_CCE_MIN_PRESS

CCE Calculation : auto minmum pressure

CALC_DIFF_PRESSURES[n] DIFF Calculation : stage pressures CALC_DIFF_TEMP[0] DIFF Calculation : temperature

CALC_COMPOS_PRESSURES[n] Composite Differential Calculation : stage pressures

CALC_COMPOS_TEMP[0] Composite Differential Calculation : temperature

CALC_CVD_PRESSURES [n] CVD Calculation : stage pressures CALC_CVD_TEMP[0] CVD Calculation : temperature CALC_DEPL_PRESSURES[n] Depletion Study Calculation : stage pressures CALC_DEPL_TEMP[0] Depletion Study Calculation : temperature CALC_SWELL_TEMPS[n] Swelling Test : temperatures CALC_SWELL_COMPS[n] Swelling Test : compositions CALC_SWELL_VOLS[n] Swelling Test : vol/vol inputs



CALC_GORCORR_SEP_PRESSURES [n] GOR/FVF Correction : Separator stage pressures

CALC_GORCORR_SEP_TEMPERATURES [n] GOR/FVF Correction : Separator stage temperatures

REGR_GORCORR_SEP_PRESSURES [n] Regression GOR/FVF Correction : Separator stage pressures

REGR_GORCORR_SEP_TEMPERATURES [n] Regression GOR/FVF Correction : Separator stage temperatures

CALC_PHASEENV_TEST_PRESSURES [n] Phase Envelope Test Points: pressures CALC_PHASEENV_TEST_TEMPERATURES [n] Phase Envelope Test Points: temperatures

CALC_SHOW_PHASEENV_TESTPTS Phase Envelope Test Points: show points flag CALC_TEST_POINT_VALUE1[n] Plot Test Points: value 1 CALC_TEST_POINT_VALUE2[n] Plot Test Points: value 2 CALC_TEST_POINT_INDEX1[n] Plot Test Points: index 1 CALC_TEST_POINT_INDEX2[n] Plot Test Points: index 2 CALC_TEST_POINT_PROCESS[n] Plot Test Points: process eg CCE CALC_BKOIL_EXPORT_COLUMN [n] Blackoil Export Calculation: column select flag CALC_BKOIL_EXPORT_TEMPS [n] Blackoil Export Calculation: table temperature CALC_BKOIL_EXPORT_PRESSURES [n][l] Blackoil Export Calculation: table pressures CALC_BKOIL_EXPORT_TABLE Blackoil Export Calculation: active table

number CALC_PHASE_ENV_CURVE_POINTS Phase Envelope Calculation: number of points

per curve CALC_PHASENV_FRACTION[n] Phase Envelope Calculation: vapour fractions

to calculate CALC_WAXTEMP_MAX_PRESS Wax Appearance Temp: auto maximum

pressure CALC_WAXTEMP_MIN_PRESS Wax Appearance Temp: auto minimum

pressure CALC_WAXTEMP_NO_PRESS_VALUES Wax Appearance Temp: auto number of

pressure values CALC_WAXTEMP_PRESSURES[n] Wax Appearance Temp: user-defined

pressures CALC_HYDRATE_MAX_TEMP Hydrate Calculation: auto maximum

temperature CALC_HYDRATE_MIN_TEMP Hydrate Calculation: auto minimum

temperature CALC_HYDRATE_NO_TEMP_VALUES Hydrate Calculation: auto number of

temperature CALC_HYDRATE_TEMPERATURES[n] Hydrate Calculation: user-defined temperatures CALC_HYDRATE_INHIBIT_CONC [n] Hydrate Calculation: inhibitor concentrations UTILS_ENTHALPY_BALANCE_START_PRESS Utility Enthalpy Balance: start pressure UTILS_ENTHALPY_BALANCE_END_PRESS Utility Enthalpy Balance: end pressure UTILS_ENTHALPY_BALANCE_END_TEMP Utility Enthalpy Balance: end temperature UTILS_ENTHALPY_BALANCE_MAX_PRESS Utility Enthalpy Balance: auto maximum

pressure UTILS_ENTHALPY_BALANCE_MIN_PRESS Utility Enthalpy Balance: auto minimum

pressure UTILS_ENTHALPY_BALANCE_NO_VALUES Utility Enthalpy Balance: auto number of

pressures UTILS_ENTHALPY_BALANCE_USER_PRESSURES

Utility Enthalpy Balance: auto number of pressures

CALC_SMALL_SEP_OILDENSITY[n] Small Separator Calc: oil density result array CALC_SMALL_SEP_OILAPI[n] Small Separator Calc: oil API result array CALC_SMALL_SEP_GOR[n] Small Separator Calc: GOR result array CALC_SMALL_SEP_GASGRAVITY[n] Small Separator Calc: gas gravity result array SLIMTUBE_NUMCELLS Slimtube calculation: Number of cells SLIMTUBE_CELL_DELTAX[n] Slimtube calculation: Delta X value for cell n SLIMTUBE_CELL_DELTAY[n] Slimtube calculation: Delta Y value for cell n SLIMTUBE_CELL_DELTAZ[n] Slimtube calculation: Delta Z value for cell n SLIMTUBE_CELL_DEPTH[n] Slimtube calculation: Depth value for cell n SLIMTUBE_CELL_PRESSURE[n] Slimtube calculation: Pressure value for cell n SLIMTUBE_CELL_PERM[n] Slimtube calculation: Permeability value for cell

n SLIMTUBE_CELL_POROSITY[n] Slimtube calculation: Porosity value for cell n

PVTP User Guide


SLIMTUBE_PRESSGRADIENT Slimtube calculation: Pressure gradient SLIMTUBE_RESOILSATN Slimtube calculation: Residual Oil saturation SLIMTUBE_GASSATN Slimtube calculation: Gas saturation SLIMTUBE_ROCKCOMP Slimtube calculation: Rock Compressibility SLIMTUBE_TEMPERATURE Slimtube calculation: Temperature SLIMTUBE_PERM_NUMINTABLE Slimtube calculation: Number of perms in table SLIMTUBE_PERM_NUMINTABLE Slimtube calculation: Number of perms in table SLIMTUBE_CELL_TABLE_SOIL[n] Slimtube calculation: Table SOIL value n SLIMTUBE_CELL_TABLE_KRO[n] Slimtube calculation: Table KRO value n SLIMTUBE_CELL_TABLE_KRG[n] Slimtube calculation: Table KRG value n SLIMTUBE_CELL_TABLE_PCGO[n] Slimtube calculation: Table PCGO value n SLIMTUBE_PRODRATE Slimtube calculation: Production rate SLIMTUBE_STARTPRESSURE Slimtube calculation: Start Pressure SLIMTUBE_INJRATE Slimtube calculation: Injection rate SLIMTUBE_INJRATEPPI Slimtube calculation: Injection rate PPI SLIMTUBE_INJPPI Slimtube calculation: Injection PPI SLIMTUBE_TIMESTEP[n] Slimtube calculation: Time step number n SLIMTUBE_NUM_TIMESTEPS Slimtube calculation: Number of time steps SLIMTUBE_CELLDATA_VALUES Slimtube calculation: Number of cell data

values SLIMTUBE_PRODCELL Slimtube calculation: Producing Cell SLIMTUBE_INJCELL Slimtube calculation: Producing Cell SLIMTUBE_PRESSURES[n] Slimtube calculation: user-defined tube

pressures SLIMTUBE_TIMESTEPS[n] Slimtube calculation: Calculated timesteps SLIMTUBE_MAXPRESSURE Slimtube calculation: auto maximum pressure SLIMTUBE_MINPRESSURE Slimtube calculation: auto minimum pressure SLIMTUBE_PRESSURE_VALUES Slimtube calculation: auto number of pressures SLIMTUBE_PRESSURE_VALUES Slimtube calculation: auto number of pressures UTILS_TARGETGOR Stream Target GOR calculation: GOR Target UTILS_TARGETPSAT Stream Target PSAT calculation: Saturation

Pressure Target UTILS_TARGETPSAT_TEMP Stream Target PSAT calculation: temperature UTILS_WATERSATN_MAXTEMP Utilities water saturation calculation: auto

maximum temperature UTILS_WATERSATN_MINTEMP Utilities water saturation calculation: auto

minimum temperature UTILS_WATERSATN_MAXPRESS Utilities water saturation calculation: auto

maximum pressure UTILS_WATERSATN_PRESSVALUES Utilities water saturation calculation: number of

pressures UTILS_WATERSATN_PRESSVALUES Utilities water saturation calculation: number of

temperatures



D6.8 Carrying out Calculations and Obtaining Results Examples of all modes and calculations are included in the sample Excel spreadsheets distributed with PVTP. The calculation to be done is set using the OPTIONS.CALC_TYPE variable. The following alternative calls can be made: BLACKOIL_OIL - Black Oil Model for Oil BLACKOIL_GAS - Black Oil Model for Gas BLACKOIL_COND - Black Oil Model for Condensate CRITPOINT - Critical Point Calculation PHASEENV - Phase Envelope Calculation PSAT – Saturation Pressure Calculation CCE – Constant Composition Expansion CVD – Constant Volume Depletion DIFF – Differential Liberation SEP – Separator Calculation COMPGRAD – Compositional Gradient Calculation SWELL – Swelling Test Calculation DEPL – Depletion Study Calculation BLACKOIL_EXPORT – Black Oil Export Table Calculation CCE_WITH_WATER - Multiphase Constant Composition Expansion SEP_WITH_WATER - Multiphase Separator COMPOS – Composite Differential Liberation MULTIPHASE – Multiphase (Wax) Flash WAXTEMP – Wax appearance Temperature HYDRATE – Hydrate Formation Pressure ISENTHALPIC_FLASH – Enthalpy Balance Calculation SLIMTUBE – SlimTube Simulation WATER_SATURATION – Water Saturation Calculation Additional calculations: FLASH – Section 8.9 Small Separator Calculation – Section 8.10 Saturation Pressure at Reference Conditions – Section 8.11 Recombination Calculations – Section 8.12 Allocation: Blending to a target GOR – Section 8.13 Important Calls: RESET_STREAM_IN_CALC_FLAGS – resets stream calculation flags prior to calculation DoCmd "PVT.KEYWORD[Wellstream]" – do calculation identified by keyword on stream index or name CALC_COLUMN_TOTAL – find number of colums calculated CALC_NUM_RESULTS – find lines of results calculated CALC_COLUMN_NAME[n] – get name of column n (zero based index) CALC_COLUMN_UNIT[n] – get unit string of column n (zero based index) CALC_COLUMN_VALUE[l][n] – get value calculated for line l and column n (zero based indices) The code fragment below is taken from OPEN_CCE_PSAT_CALC.XLS and shows the basics of setting up and initiating a calculation.

PVTP User Guide


' Identify the mode to be used in the calculation USER or AUTO SendCellData "PVT.CALCUL[" + CStr(iStream) + "].CALC_CCE_MODE" If (Worksheets(Sheet).Cells(10, 2) = "AUTO") Then iLine = 13 'AUTO Mode 'send calculation ranges SendCellData "PVT.CALCUL[" + CStr(iStream) + "].CALC_CCE_MIN_TEMP" SendCellData "PVT.CALCUL[" + CStr(iStream) + "].CALC_CCE_MAX_TEMP" SendCellData "PVT.CALCUL[" + CStr(iStream) + "].CALC_CCETEMPVALUES" SendCellData "PVT.CALCUL[" + CStr(iStream) + "].CALC_CCE_MIN_PRESS" SendCellData "PVT.CALCUL[" + CStr(iStream) + "].CALC_CCE_MAX_PRESS" SendCellData "PVT.CALCUL[" + CStr(iStream) + "].CALC_CCEPRESSVALUES" Else iLine = 23 ' USER Mode ' send individual temperatures and pressures For iCalc = 0 To 9 DoSetStr iLine, 1, "PVT.CALCUL[" + CStr(iStream) + "].CALC_USER_CCE_TEMPS[" + CStr(iCalc) + "]", False For iCol = 0 To 4 DoSetStr iLine, 2 + iCol, "PVT.CALCUL[" + CStr(iStream) + "].CALC_USER_CCE_PRESSURES[" + CStr(iCalc + (10 * iCol)) + "]", False Next iLine = iLine + 1 Next End If ' Clear the stream calculation flags DoCmd "PVT.RESET_STREAM_IN_CALC_FLAGS" ' Tell the program to do a CCE Calculation on stream identified by index iStream DoCmd "PVT.CCE[" + CStr(iStream) + "]"

The first section reflects the CCE input dialog, sending the mode the calculation is to operate with and the temperatures| pressures to be used. All that is required then is to clear any existing calculation flags and to initiate the command using the keyword from the list above. Note that the calculation has been set up to do one stream at a time. To do multiple streams call the command again with a different stream index|name. Once the calculation is complete, any of the columns calculated can be accessed as shown in the code fragment below:

'Find the number of results produced during the calculation iNumRes = DoGetCheck("PVT.CALCUL[" + CStr(iStream) + "].CALC_NUM_RESULTS") 'Find the number of columns calculated for CCE iNumCols = DoGetCheck("PVT.CALC_COLUMN_TOTAL") For iCol = 0 To iNumCols - 1 'Get column names Worksheets(Sheet).Cells(iLine, iCol + 1) = DoGet("PVT.CALC_COLUMN_NAME[" + CStr(iCol) + "]") 'Get column units Worksheets(Sheet).Cells(iLine + 1, iCol + 1) = DoGet("PVT.CALC_COLUMN_UNIT[" + CStr(iCol) + "]") For iRes = 0 To iNumRes - 1 'get all column values Worksheets(Sheet).Cells(iLine + iRes + 2, iCol + 1) = DoGet("PVT.CALCUL[" + CStr(iStream) + "].CALC_COLUMN_VALUE[" + CStr(iRes) + "][" + CStr(iCol) + "]") Next Next

The calculation results form a table which is normally displayed in PVTP results dialog.The first step is to find the number of lines calculated using CALC_NUM_RESULTS. The number of columns available for this calculation can then be retrieved using CALC_COLUMN_TOTAL. Individual column names and units are found by calls to CALC_COLUMN_NAME and CALC_COLUMN_UNIT with a zero-based index for the column number. Repeated calls to CALC_COLUMN_VALUE is then used to fill in the table.



D6.8.1 Analysis Analysis is available with most calculations. This data can be retrieved using code like the segment below: ' Get analysis number iRes Worksheets(Sheet).Cells(4, 2) = iRes ' display the analysis block temperature and pressure iErr = DisplayCellData("Temperature", DoGetCheck("PVT.CALCUL[" + CStr(iStream) + "].CALC_ANALYSIS[" + CStr(iRes) + "].STAGE_TEMP")) iErr = DisplayCellData("Pressure", DoGetCheck("PVT.CALCUL[" + CStr(iStream) + "].CALC_ANALYSIS[" + CStr(iRes) + "].STAGE_PRESS")) Worksheets(Sheet).Range("A10:E200").ClearContents 'find number of components iNumComp = DoGetCheck("PVT.STREAMRUN[" + CStr(iStream) + "].NUMCOMPONENTS") iLine = 10 For icomp = 0 To iNumComp - 1 ' get component name liquid composition vapour composition and K values Worksheets(Sheet).Cells(iLine + icomp, 1) = DoGet("PVT.STREAMRUN[" + CStr(iStream) + "].COMPONENT[" + CStr(icomp) + "]") Worksheets(Sheet).Cells(iLine + icomp, 2) = DoGetCheck("PVT.CALCUL[" + CStr(iStream) + "].CALC_ANALYSIS[" + CStr(iRes) + "].LIQUID_COMPOSITION[" + CStr(icomp) + "]") Worksheets(Sheet).Cells(iLine + icomp, 3) = DoGetCheck("PVT.CALCUL[" + CStr(iStream) + "].CALC_ANALYSIS[" + CStr(iRes) + "].VAPOUR_COMPOSITION[" + CStr(icomp) + "]") Worksheets(Sheet).Cells(iLine + icomp, 4) = DoGetCheck("PVT.CALCUL[" + CStr(iStream) + "].CALC_ANALYSIS[" + CStr(iRes) + "].KVALUES[" + CStr(icomp) + "]") Next iLine = iLine + iNumComp ' Get Extra data iErr = DisplayCellData("Percent Vapour", DoGetCheck("PVT.CALCUL[" + CStr(iStream) + "].CALC_ANALYSIS[" + CStr(iRes) + "].VAP_PERCENT")) iErr = DisplayCellData("Percent Liquid", DoGetCheck("PVT.CALCUL[" + CStr(iStream) + "].CALC_ANALYSIS[" + CStr(iRes) + "].LIQ_PERCENT")) iErr = DisplayCellData("Oil Gravity", DoGetCheck("PVT.CALCUL[" + CStr(iStream) + "].CALC_ANALYSIS[" + CStr(iRes) + "].OIL_GRAVITY")) The individual analysis blocks are accessed via the label CALC_ANALYSIS[n] where n is a zero-based index. Data is devided into identification eg. STAGE_TEMP or STAGE_DEPTH component data such as vapour composition K values etc. or extra data such as Oil_GRAVITY , TOTAL_GOR etc. The data available is listed below:

STAGE_TEMP Analysis Temperature STAGE_PRESS Analysis Pressure STAGE_DEPTH Analysis Depth TOTAL_COMPOSITION[n] Total Composition for

component[n] VAPOUR_COMPOSITION[n] Vapour Composition for

component[n] WATER_COMPOSITION[n] Waterl Composition for

component[n] LIQUID_COMPOSITION[n] Liquid Composition for

component[n] LIQUID_COMPOSITION2[n] Liquid 2 Composition for

component[n] - Multiphase LIQUID_COMPOSITION3[n] Liquid 3 Composition for



component[n] - Multiphase

PVTP User Guide


SOLID_COMPOSITION[n] Solid Composition for component[n]

ACCVAP_COMPOSITION[n] Accum. Vapour Composition for component[n]

KVALUES[n] K Values for component[n] VAP_PERCENT Mole Percent Vapour LIQ_PERCENT Mole Percent Liquid ACCUM_PERCENT Mole Percent Accum.

Vapour OIL_GRAVITY Oil Gravity TOTAL_GOR Total GOR STAGE_GOR Stage GOR GAS_GRAVITY Gas Gravity STAGE_GROSS_HV Stage Gross Heating Vaue STAGE_NET_HV Stage Net Heating Vaue ACCUM_GROSS_HV Accum. Gross Heating

Vaue ACCUM_NET_HV Accum Net Heating Vaue

D6.9 Flash Calculation The two-phase flash calculation is a key part of any EoS calculation package. The majority of calculations e.g. constant volume depletion or separator are constructed from a series of flash calculations. To increase the flexibility of using the OPENSERVER capabilities with PVTP , the flash calculation has been made accessible to the user. The core of the flash commands is given in the code segment below, which is taken from the Excel spreadsheet OPENPVT.XLS. ' Tell program which temperature and pressure to flash at SendCellData "PVT.STREAMRUN[" + CStr(iStream) + "].RUNTEMP" SendCellData "PVT.STREAMRUN[" + CStr(iStream) + "].RUNPRESS" 'Do flash calculation DoCmd "PVT.FLASH[" + CStr(iStream) + "]" iLine = iLine + 2 'display compositions and results DisplayRuntimeComponentData All the work of flash is done within the STREAMRUN structure and as such is done with a temporary, intermediate type of data. The sequence followed is as follows.

Set up the compositions and properties within the STREAMRUN structure Send the required flash temperature and pressure to RUNTEMP and

RUNPRESS respectively Perform flash using the FLASH command Read the vapour and liquid compositions and K values calculated from

STREAMRUN Read the other calculated data eg. Vapour fraction,z factors phase densities

etc. from STREAMRUN . A Visual Basic file (FlashDemo.*) which gives illustrates doing a flash is also distributed with PVTP.

D6.10 Small Separator Calculation



The small separator calculation is called from the small calculation dialog within PVTP. The inputs to it are the same as the larger separator calculation, but the calculat


D6.11 Saturation Pressure at Reference Calculation The Saturation Pressure at Reference calculation is called from the small calculation dialog within PVTP. The use of this calculation is illustrated in OPEN_CCE_PSAT_CALC.XLS from which the code fragment below is taken:

SendCellData "PVT.STREAMRUN[" + CStr(iStream) + "].RUNTEMP" DoCmd "PVT.SINGLE_PSAT[" + CStr(iStream) + "]" iLine = 7 iErr = DisplayCellData("PSAT", DoGetCheck("PVT.STREAMRUN[" + CStr(iStream) + "].RUNPRESS"))

The use of this calculation is very styraightforward. Place the temperature required in RUNTEMP. Then call the calculation using the SINGLE_PSAT command. The resulting saturation pressure will be placed in the RUNPRESS variable.

D6.12 Recombination Calculations The PVTP program contains 2 recombination calculations whch are accessed via the Data|Select Components dialog. The 2 modes available are: Simple: where compositions of 1 separator vapour are combined with stock tank oil ans gas to give the recombined composition and Extended: where up to 5 separator compositions can be used. Both modes can be run via the OPENSERVER using the following commands.

RECOMBINE_SIMPLE[n] Perform the simple recombination

on stream n RECOMBINE_COMPLEX[n] Perform the complex recombination

on stream n COPY_RECOMBINE_COMPOSITION Overwrite the current

STREAMBASE composition with the one calculated by recombination

It should be noted that the recombination data is held within the STREAMBASE structure. If you wish to calculate with this composition it must be transferred to the STREAMRUN area. An example of how the recombine data is read and set is distributed in the OPEN_RECOMBINATION.XLS sample file. The code segment below is taken from this file:

DoSet "PVT.STREAMBASE[" + CStr(iStream) + "].RECOM_STOCKTANK_GOR", CStr(ThisGOR) DoCmd "PVT.SET_ACTIVE_STREAM[" + CStr(iStream) + "]" DoCmd "PVT.RECOMBINE_SIMPLE[" + CStr(iStream) + "]" DoCmd "PVT.COPY_RECOMBINE_COMPOSITION[" + CStr(iStream) + "]" DoCmd "PVT.COPYSTREAMBASE_TO_STREAMRUN" Temp = Worksheets(Sheet).Cells(10, 7) DoSet "PVT.STREAMRUN[" + CStr(iStream) + "].RUNTEMP", CStr(Temp) DoCmd "PVT.SINGLE_PSAT[" + CStr(iStream) + "]" Press = DoGet("PVT.STREAMRUN[" + CStr(iStream) + "].RUNPRESS")

In this segment a recombination is done on the basis of a changing recombination GOR. The recombined composition is then copied to STREAMBASE and then to STREAMRUN. Once in runtime it is used to find the saturation pressure of the recombined fluid using the calculation described in section 8.9. The sequence followed is



PVTP User Guide

Set a new recombination GOR via the RECOM_STOCKTANK_GOR variable Make the selected stream the current one using the SET_ACTIVE_STREAM

command Calculate the recombination using the RECOMBINE_SIMPLE command Overwrite the stream composition with the result of the recombination using

COPY_RECOMBINE_COMPOSITION Copy composition to STREAMRUN to allow calculation to be done Set the temperature at which PSAT is to be calculated Do saturation pressure calculation Read result which is in RUNPRESS

D6.13 Allocate: Blending to a target GOR The allocation calculation is called from the stream menu in PVTP. The use of this calculation is illustrated in OPEN_ALLOCATE_BLEND.XLS from which the code fragment below is taken:

Worksheets("Allocate").Cells(3, 4) = DoGet("PVT.STREAMBASE[" + CStr(iStream) + "].STREAMNAME[0]") Worksheets("Allocate").Cells(4, 4) = DoGet("PVT.STREAMBASE[" + CStr(iStream2) + "].STREAMNAME[0]") iLine = 10 SendCellData "PVT.CALCUL[" + CStr(iStream) + "].UTILS_TARGETGOR" DoSet "PVT.CALCUL[" + CStr(iStream) + "].CALC_SECOND_STREAM", iStream2 iLine = 12 SendCellData "PVT.OPTIONS.CREATE_MAX_ITERATIONS" SendCellData "PVT.OPTIONS.CREATE_GOR_END_TEST" DoCmd "PVT.CALCULATE_BLEND_GOR[" + CStr(iStream) + "]" DoCmd "PVT.UPDATEDISPLAY" iLine = 31 iErr = DisplayCellData("Mole Percent Blend Stream 1", DoGet("PVT.STREAMRUN[" + CStr(iStream) + "].MOLE_PERCENT1_BLEND_GOR")) iErr = DisplayCellData("Mole Percent Blend Stream 2", DoGet("PVT.STREAMRUN[" + CStr(iStream) + "].MOLE_PERCENT2_BLEND_GOR")) iErr = DisplayCellData("Weight Percent Blend Stream 1", DoGet("PVT.STREAMRUN[" + CStr(iStream) + "].WEIGHT_PERCENT1_BLEND_GOR")) iErr = DisplayCellData("Weight Percent Blend Stream 2", DoGet("PVT.STREAMRUN[" + CStr(iStream) + "].WEIGHT_PERCENT2_BLEND_GOR")) The sequence followed is Set up the streams to be used Send the target GOR to be matched Setup the calculation limits if required Send the CALCULATE_BLEND_GOR command. Retrieve the results from the MOLE_PERCENT1_BLEND_GOR etc. variables

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