tutorial severeslugging

LedaFlow Tutorial 2014

LedaFlow Tutorial

Study of severe slugging effects in a

Pipeline/Riser geometry


Table of contents

Sommaire Introduction ............................................................................................................................................. 1

Create a database .................................................................................................................................... 2

Create a case ........................................................................................................................................... 3

Set PVT option ......................................................................................................................................... 6

Set heat transfer option .......................................................................................................................... 9

Define the pipe wall properties ............................................................................................................. 10

Set pipe geometry ................................................................................................................................. 13

Configure mesh ..................................................................................................................................... 15

Set boundary conditions ....................................................................................................................... 17

Set numerical parameters ..................................................................................................................... 18

Run the case .......................................................................................................................................... 20

Plot and export the results .................................................................................................................... 21


1

Introduction This tutorial has been designed to study the severe slugging effects found in a simple geometry, using water and air at atmospheric pressure. The document teaches step by step the basic features of LedaFlow: from creating a database and a new case to analysing the obtained results. Geometry This tutorial will be based on a previous report written by J.Fabre et al for the Society of Petroleum Engineers, published in 1987 (SPE 16846).. The following figure represents the geometry of the pipeline that will be used during this exercise.

Device characteristics

Pipe diameter 53mm in the entire system

Pipe geometry Pipeline of 25m riser of 13.5 m 50 cm radius bend

Pipe walls 5 mm of steel 5 mm of an insulation material 5 mm of an isolated coating

Ambient temperature 20 C

Inlet conditions Gas mass flow rate: 0.000533 kg/s Water mass flow rate: 0.280167 kg/s

Outlet conditions 1 bar 20 C

0

2

4

6

8

10

12

14

0 5 10 15 20 25

Z -

Pip

e h

eig

ht

(m)

X - Pipe length (m)

Pipeline/Riser geometry


2

Create a database

LedaFlow uses a MySQL version 5.1 as a database service. The user has the possibility to create

several databases inside MySQL to organise data. The database management tool allows the user to

manage all the databases and their contents.

Go to the Tools menu

Click on Database management

Click on the Databases tab

Create a new database by clicking on the Add new icon


3

Name the database severeslugging

Click on Close once the database has been created. Your case will be saved in this

database.

Note: LedaFlow saves automatically all changes and results. You do not need to save it manually.

Create a case

Create a new folder called SevereSlugging in the Case Browser: Right-click on the default folder Project and select Rename

Enter the name SevereSlugging and click OK


4

Create a default case Right-click on the folder SevereSlugging and select New case

Select Leda 1D - 2phases

Enter the name SevereSlugging Case and click OK

A default 2-phase case has been created.


5

Rename the pipes and nodes: Right click on the pipe and select Rename

Rename pipe from Pipe 1 to Flowline

Similarly rename Node 1 to Manifold and Node 2 to Outlet


6

Set PVT option For this exercise, the user must set the thermodynamics options in order to run the calculation because we use a water-air mixture. The user could you use a specific PVT table or introduce the thermodynamic variables as constants among other options. In this tutorial the above-mentioned case will be explained.

Open the Case setting window

The following window appears.


7

The first case is using the PVT table.

Load a PVT table

Click on the green plus sign under PVT Library

Click on the folder icon and search for the file PVT.inp Name the table PVT

The other option is set the thermodynamic variables as constants.

Click on the green plus sign under PVT Library

Click on Type and select constant

Introduce the values manually.

Name the table PVT

Comment [AV1]: Tambien agregar nuestro caso, que es cuando metemos los valores manuelmente.


8

Change the PVT object assigned to Flowline

Double-click on Flowline in PVT selection

Select PVT from the drop-down menu


9

Set heat transfer option LedaFlow includes several options for heat transfer modelling: U Value, walls and dynamic walls. According to the option selected, the user will have to set up the wall properties.

Select the Model options tab in the Case settings window Select the option Yes for the Temperature calculations options. This activates the energy

equation in LedaFlow Select Walls (dynamic) as the Wall heat transfer option. This will instruct LedaFlow to

account for heat storage in the pipe walls

The following window appears


10

Define the pipe wall properties

Define the pipe wall properties by clicking on the Walls library icon

Create new materials in the Material option

Add a new material by clicking on . Give the new material the name Isolated

Change properties of all materials

Isolated Insulation Steel

Density (kg/m3) 1300 500 1300

Conductivity (W/m.K) 0.2 0.03 0.16

Heat capacity (J/kg.K) 1500 1000 1500

Click on the Walls option

Add a new wall by clicking on close to Wall1 Name the wall FlowlineWall

Comment [AV2]: Actualizar Procedimiento


11

Under Wall layers option, click twice on to add two new layers Select the material Steel for the first layer, Insulation for the second one and Isolated

for the last one Set a thickness of 5 mm for each layer


12

Click on Save All


13

Set pipe geometry

Set the geometry for the pipe Click on the Pipe Properties located in the main toolbar

LedaFlow opens the following window, where you can edit the pipeline geometry and properties.

Open the Excel file that contains the geometry of the pipeline for this case

Copy the content of the file and paste it in the Pipe Properties window

Under the Walls column, double-click on Wall1 and change the assigned wall to FlowlineWall. Do so for all geometry points to have the same wall all over.

Once the geometry is set, click on Ok. The following message appears


14

The aim of this message is to warn the user that any changes on the geometry will affect the

mesh and the simulation results. Make sure that your geometry is well defined before

running the case

Click on Yes to continue

The geometry can be seen under LedaFlow


15

Configure mesh The mesh is the discretization of the geometry for numerical computation.

Set the mesh for the pipe by clicking on the Edit mesh in construction icon

Click on the Lock Geom points button

Choose the Uniform Method under the Grid constructor case

Set the approximate number of cells to 210

Click on Run


16

The following graph shows the geometry, the meshing and the L-Ratio of the S-Riser system

If you change the geometry in the Pipe Properties Window, you will have to update the meshing to continue What is the LENGTH RATIO? It is the ratio between the length of two consecutive cells and it is really important to keep it lower than 2 to run the calculation. Otherwise, LedaFlow will send a warning message. In any case, start the simulation with a fine mesh, like the one you have just created, and then try to simplify it. However, it is not advisable to have long cell lengths near the base of the riser and within the catenary. The idea is to be able to account for the filling and emptying of the base of the pipe, and if cells are too long, this effect may not be observed correctly.


17

Set boundary conditions LedaFlow can handle mass-pressure and pressure-pressure boundary. The split can be either calculated automatically by flashing the fluid at the inlet or set through the volume or mass fractions of each phase

Set the inlet Gas

Right click on the inlet node

Click on Properties

Choose No for the flash inflow option Set the following characteristics for the inlet

Time (s) 0

Ft (kg/s) 0.2807

mg (-) 0.0019

ml (-) 0.9981

Temperature (C) 20


18

Set the outlet

Right click on the outlet node Click on Properties

Set the following characteristics for the outlet

Set numerical parameters

LedaFlow is using a dynamic time step which means the size of the time step depends on the grid and

the velocities through the CFL number.

The numerical settings are defined by: the maximum time step, the CFL number, the sample rate and

the time to advance the solution.

Click on the Numerical settings tab in the Case settings window

Set the following parameters

Simulation time (s) 1000

Sample time (s) 1

CFL 0.8

Dtmax 0.05


19


20

Run the case

Initialise your case

You can see the progress in the bottom bar:

Run your case

Once LedaFlow has finished simulating the case, the progress bar will be complete. If you go to the

Output tab, under the Status window, you can see the errors encountered (if any) and a review of

the simulation numerical results.


21

Plot and export the results

You can visualise the terrain slugging effect by plotting the pressure as a function of time for the lowest point of the pipe. This point is the most interesting one, because it is where the liquid accumulates and does not let the gas go through.

To create a plot, click on the Create a new plot icon on the toolbar.

There are several plotting possibilities.

Select Trend from the Plot Type drop-down menu

Make sure that Flowline is selected under the Plot Object list

Under the Templates tab, ungroup PT and phase mass flowrates by clicking on the [+] sign


22

Select Pressure to plot pressure evolution with time for this pipe

You can also choose Pressure from the Select Variables tab.

Once you click Ok, a new window will be opened where you will see the simulation results. By default, LedaFlow plots the trend of the first mesh cell. You will need to instruct LedaFlow to show you the results for the lowest point of the pipe.

To do so, click on the Edit Position icon on the toolbar located on the up-left corner of the new window.


23

In the new window that appears, drag the position bar to reach the bottom of the pipe, at 25.1277 m (cell number 148).

Click on Ok. LedaFlow will plot the pressure trend on this point. To export the results to a .csv format, click con the Export data to .csv file icon on the toolbar.

This will allow you to work on the results in other software, like Excel.

Congratulations, you have finished the tutorial. Analyse the results of the simulation in terms of

pressure amplitudes and slugging periods.

What should be the amplitude expected?

What parameter controls the slugging periods?

Verify that all boundary conditions are respected (mass flow rates, temperatures, etc.)

Reproduce the same simulation with the following boundary conditions

Sup. Velocity at Std Conditions (m/s)

Case 1 Case 2

Gas 0.45 2.24

Water 0.127 0.127

Compare simulated results with experimental data provided by the paper


24

Annexe

Example of a geometrie for this tutorial

X [m] Y

[m] Z

[m] Diameter

[mm] Roughness

[mm] Tout [C]

Hout [W/m2-K] Walls[]

0 0 0,25 53 2 6,85 1000 Wall1

5 0 0,2 53 2 6,85 1000 Wall1

10 0 0,15 53 2 6,85 1000 Wall1

15 0 0,1 53 2 6,85 1000 Wall1

20 0 0,05 53 2 6,85 1000 Wall1

22 0 0,03 53 2 6,85 1000 Wall1

24,1 0 9 53 2 6,85 1000 Wall1

24,3 0 7 53 2 6,85 1000 Wall1

24,5 0 5 53 2 6,85 1000 Wall1

24,7 0 3 53 2 6,85 1000 Wall1

25 0 0 53 2 6,85 1000 Wall1

25,1 0 5 53 2 6,85 1000 Wall1

25,2 0 9 53 2 6,85 1000 Wall1

25,3 0 15 53 2 6,85 1000 Wall1

25,35 0 0,02 53 2 6,85 1000 Wall1

25,4 0 0,03 53 2 6,85 1000 Wall1

25,45 0 0,04 53 2 6,85 1000 Wall1

25,48 0 48 53 2 6,85 1000 Wall1

25,49 0 0,06 53 2 6,85 1000 Wall1

25,5 0 0,08 53 2 6,85 1000 Wall1

25,5 0 7 53 2 6,85 1000 Wall1

25,5 0 13,5 - - 6,85 1000 -

tutorial severeslugging

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