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Gas Lift WorkshopSingapore

7-11 February 2011

Juan Carlos Mantecon –

API RP 19G11 Dynamic Simulationof Gas Lift Wells and Systems

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CONTENT

• This presentation describes dynamic simulation and its current applications for gas-lift wells and systems.

• It gives an overview of the new (in draft format) API Recommended Practice for Dynamic Simulation of Gas-Lift Wells and Systems: API RP 19G11.

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API RP 19G11 • This API Recommended Practice covers the application of

dynamic simulation for gas-lift wells and systems.• Dynamic simulation is an important tool to assist in the

design, operation, surveillance, troubleshooting, anddiagnosis of gas-lift processes.

• Most gas-lift design and diagnosis programs have usedsteady-state models. This may lead to inappropriate designsand inefficient operations because gas-lift wells and systemsare seldom steady. Gas-lift wells usually exhibit dynamicpressure and flow rate fluctuations.

• It is important to understand the dynamic behaviour of wellsand systems so they can be more appropriately designed,operated, and diagnosed.

• Although the primary focus is currently on gas-lift, this API-RP addresses a broad range of artificial lift systems and topics

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API RP 19G11 – WORK GROUP MEMBERS

20 members representing 16 companies and one universityJuan Mantecon, SPT Group - ChairpersonCleon Dunham, Oilfield Automation - SecretaryAdam Ballard, BPArne Valle, Knud Lunde, StatoilHydroBoots Rouen, SchlumbergerDan Dees, AppSmithsEric Laine, Laine ConsultingFernado Ascencio Candejas, PEMEXDr. Fernando Samaniego, UNAM (Mexico Autonomous Nacional University) Galileu Paulo Henke A. Oliveira, PetrobrasGreg Stephenson, OccidentalKallal Arunachalam, ConocoPhillipsKen Decker, Decker TechnologyMurat Kerem, ShellOctavio Reyes, TechnipShanhong Song, ChevronWayne Mabry, ShellYaser Salman, YAS Petroleum Eng.Yula Tang, Chevron

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DYNAMIC SIMULATION

• The application of multiphase flow transient numerical simulation (dynamic simulation) techniques in wells and production systems has become an important methodology to ensure:

─ Wells/field life cycle sound engineering design,

─ Optimal operation guidelines,─ Optimization of investment and

operating costs,─ Production optimization, and─ Minimization of risk, safety hazards,

and environmental impact.

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DYNAMIC SIMULATION

• Dynamic simulation can be used at any stage of a field’s life cycle to build a virtual model of a well and/or production system.

• It can help to understand transient well behaviour and determine the optimum process to eliminate or minimize instability problems.

• It can be used to analyse "what if" scenarios and predict results.

• It does not replace NODAL® analysis but fills gaps where steady-sate analysis techniques cannot provide adequate solutions.

P12

P11

P10

P9

P8

P7

P6

P5

P4

P3

P2

P1

1 2 543

1 2 543

1,2,3,…,5 (inside) : section volumes

1,2,3,…,6 (outside): section boundaries

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•The weak points of NODAL S.S. analysis comparing with dynamic (transient) simulation are:

• Unable to predict severe slugging introduced by riser / flowline or / sinusoidal wellbores

• Unable to perform instability analysis• Unable to performance gas-lift unloading analysis• Unable to predict dynamic behaviour of plunger lift• Unable to look at gas/condensate gas well liquid load-up issues

NODAL® vs. DYNAMIC SIMULATION

• Unable to performance flow assurance study, e.g., start-up / shut-down, corrosion / chemical injection

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DYNAMIC SIMULATION for WELL DESIGN

Well design:Understand effects of well design & associated dynamic effects on well operations, including:• Vertical wells• Horizontal / Sinusoidal wells• Multi-lateral wells

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DYNAMIC SIMULATION RECOMMENDED AREAS OF USE

Gas-lift unloading / plunger lift

Instablility / Severe Slugging

Gas-lift design and optimisation

Cross-flow analysis

Gas well Liquid load-up

Well Clean-up / start-up

Well Testing: Wellbore Storage effects / Segregation effects

Wellbore thermal calculations

Flow Assurance

Inhibitor requirements

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DYNAMIC SIMULATION APPLICATIONS

• One of the relevant areas of application is for gas-lift wells and systems.

• In particular, it is useful for subsea and deepwater gas-lift wells, where transient issues related to flow assurance, complex wellbore profiles, long flowlines, and risers play a significant roll in gas-lift system design and production optimization.

Mud line

Sea level

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DYNAMIC GAS LIFT APPLICATIONS

• Continuous gas-lift / Gas-lift valve performance• Intermittent gas-lift• Gas-assisted plunger lift• Dual gas-lift• Single-point gas-lift• “Auto” gas-lift (gas from one zone is used lift other zones)• Riser gas-lift• Gas-lift for gas well deliquification• Gas-lift unloading• Kick-off of gas-lift wells• Use of gas-lift for wellbore clean-up• Gas-lift system distribution with various types of system

configurations• Use of un-dehydrated gas• Use of non-hydrocarbon gases such as CO2 and N2.

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Modelling concerns:

a) Annular Flow

b) Heat Transfer

c) Non-constant Composition in Tubing above Injection Point

Mud line

Sea level

d) Unloading Valves Operation

TYPICAL GAS LIFT WELL CONFIGURATION

Gas Lift is clearly a transient problem

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Well Clean-up – Case Study

• Estimate the minimum rate and time required to clean-up the well – Horizontal Oil Well

• Verify the planned well clean-up and testing program using dynamic simulation

Problem Description

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Well Clean-up – Case Study: NO GAS LIFT

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Well Clean-up – Case Study: GAS LIFT

When using gas lift (300 scf/min of N2during the first 4 hrs), it took 4.3hrs to clean the well.

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Well Clean-up – Case Study

• It was found that a mud plug was form at the base of the vertical section of the well which could not be lifted using the planned choke opening program.

• The injection of N2 at the base of the riser was simulated to evaluate if the amount of N2 in cylinders required to produce the well was realistic or other methodology should be considered

• When using gas lift (300 scf/min of N2 during the first 4 hrs), it took approximately 4.3 hours to clean-up the well.

• Risk and uncertainty were reduced and value added to the ROI required for a successful clean-up and well test

Problem Solutions

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Integrated Modelling ApplicationAll-in-One Gas Lift ExampleReservoir-Well-GL-Flowline-Riser-Separator-Facilities

W1 W2 W3 W4

PCV

LCV

Production Separator

PC

LC

Gas Outlet

Liquid Outlet

Emergency Liquid Outlet

Emergency Drain Valve

ID=2 m, Length=6 mNLL=0.842 mHHLL=1.687LLLL=0.315

Riser

Annulus

Gas LiftID=8-in, Depth=120 m

ID=8-in, Length=4.6 km

Depth=2840 m

Tubing ID=0.1143 m

ID=0.2159 m

• Quasi-dynamic Reservoir: incorporated explicitly

• Facilities: Simple model

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Gas

rat

eIntegrated Modelling ApplicationGas Lift ExampleReservoir-Well-GL-Flowline-Riser-Separator-Facilities

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Example: Using a DS for Unloading GL Wells

• Data provided by a well with 6 gas lift valves and a gas injection valve.

GLV details

Valve Depth (m)

Size R Dome Pressure

(bara)1 761 20/64” 0.104 105.4

2 1327 20/64” 0.104 110.3

3 1651 20/64” 0.104 112.8

4 1795 20/64” 0.104 113.4

5 1921 20/64” 0.104 113.9

6 2049 20/64” 0.104 114.4

7 2192 24/64” - -

Well ProfileElevation profile

PRODUCTION_TUBING

Ele

va

tio

n [

m]

500

0

-500

-1000

-1500

-2000

-2500

-3000

Length[m]Helix RDS Well Instability - Kick-of f Gas Simulations - T14

5000450040003500300025002000150010005000

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3

2

1

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Example: Using a DS for Unloading GL Wells

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Example: Using a DS for Unloading GL Wells

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INFORMATION PROVIDED BY DYNAMIC SIMULATION

Slugging flow:• Understand slugging flow effects and the impact on well performance• Understand when, where, and under which conditions slug flow is

originated• Understand how slug flow conditions can be minimized or eliminated

Water and/or hydrates:• Understand the effects of accumulated water and hydrates in lines,

gas-lift valves, etc.• Understand the effects of water-induced corrosion and how this can

affect stability.• Understand when, where, and under which conditions hydrates may

be formed.

Production chemistry:• Understand the effects scale, wax, and/or paraffin formation and the

impact of this on well performance and stability. SSSV location.

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INFORMATION PROVIDED BY DYNAMIC SIMULATION

Gas-lift valve performance:• Understand information for dynamic gas-lift valve optimum location

and orifice performance – design/troubleshootingWell equipment:• Understand the effects of downhole pressure restrictions such as

safety valves, corrosion deposits, scale deposits, wax deposits• Understand the effects of tight spots or holes in the tubing• Understand the effects of risers• Understand the effects of surface equipment such as flowlines,

manifolds, separators, separator back-pressure, etc.Well design:• Understand the effects of well design and the associated dynamic

effects on well operations. This includes:• Vertical wells• Horizontal wells• Multi-lateral wells• Understand when and where to inject gas into a well: in the vertical,

in the knee, in a rat hole, in the horizontal section

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THE API RP 19G11 DRAFT DOCUMENT

Table of ContentsThis document contains nine chapters to assist the gas-lift industry in understanding and applying dynamic simulation for gas-lift wells and systems:

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THE API RP 19G11 DRAFT DOCUMENTTable of Contents

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THE API RP 19G11 DRAFT DOCUMENT

Summary of RP (17 pages)

• After reading this summary chapter, the reader should understand the RPs that need to be followed to successfully use and deploy dynamic simulation of gas-lift wells and systems.

• A reference on where to turn in the document for more detailed information is provided.

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THE API RP 19G11 DRAFT DOCUMENT

Status od API 19G11

• The document can now be used in its current draft form, by anyone who wishes to use it. This means that anyone will be able to download it from ALRDC website. The API won’t sell it in its draft form and will provide it to people free of charge.

• The draft document is copyrighted.

• API will begin immediately to move the document through the balloting, final editing, and publication process.

• Once it has been finalized by API, we will begin the process to edit the document.