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Feb. 6, 2001 2001 ASME/API Gas-Lift Workshop 1

2001 ASME/API Gas-Lift Workshop

Testing and Modeling Gas-Lift Valves

by

Ken Decker, Decker Technology

Cleon Dunham, Oilfield Automation Consulting


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Testing and Modeling

Gas-Lift Valves

Outline Gas-lift valves are important

API Recommended Practice 11V2 Gas-lift Valve Performance Clearinghouse (VPC)

VPC members

Valves tested by VPC

Typical VPC results How member companies use VPC results

Future plans


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Gas-Lift Valves

Are Important

Gas-lift valves are needed to: Allow gas-lift wells to unload (work down) to the

desired operating depth Remain open and transmit enough gas to allow

transfer to the next valve

Remain in good condition during unloading Not be eroded by completion fluid

Close and remain closed when lifting from deeper Not leak

Not allow well fluids to back flow into the annulus

Re-open when needed for re-start (kick off)


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API Recommended

Practice 11V2

Prior to API RP 11V2: Gas-lift valve open/close calculations based on

steady state force/balance equation Gas passage based on Thornhill-Craver

These didn't represent real performance in dynamicoperation

Gas-lift designers were forced to use rules of thumb

API RP 11V2 published in January, 1995 Provided standards for gas-lift valve testing & modeling

But offered no specific process to implement thesestandards on a routine basis


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Gas-Lift Valve Performance

Clearinghouse (VPC)

VPC formed in 1996 as JIP (joint industryproject) to test & model valves

VPC tests a gas-lift valve to determine: When it will open/re-open under dynamic conditions

How far it will open under various upstream &downstream pressure conditions

How much gas it will transmit at each opening

When it will close under dynamic conditions If a valve does not open, move, or close correctly,

this is detected

Typically, one example valve of each type ormodel is tested


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Gas-Lift Valve Performance

Clearinghouse (VPC)

Based on these tests, the VPC developsaccurate gas-lift valve performance models

To develop these models, the VPC determines: Accurate opening pressure, at operating temperature

Accurate closing pressure, at operating conditions

Flow characteristic (Cv) of valve

Load rate of bellows and/or spring

Maximum effective stem travel

These models can be used for: Gas-lift design

Gas-lift performance analysis

Comparing actual vs. theoretical performance


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Original and Current Members

of the VPC

VPC Member Companies

Initial Members 2001 Members

Chevron Chevron

Edinburgh Petroleum Services Exxon/Mobil (pending)

Exxon PDVSA (pending)

Shell International Shell International

Weatherford Weatherford


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Gas-Lift Valves Tested

and Modeled by the VPC

Gas-Lift Valves and Orifices Tested/Modelled by the VPC Through 2000

1" IPO Gas-Lift Valves

Altec AT1-CF, Camco BK, Weatherford R-1, Weatherford R-1BL, Camco/Merla NM-16R,

McMurry Macco R-1D, McMurry Macco JR-STDN, McMurry Macco C-1

1" PPO Gas-Lift ValvesCamco BKF-6, Camco BKR-5, Camco SRF-10, McMurry Macco RF-1, Weatherford RF-1BL

1" Alternative Operation Gas-Lift Valves

Altec AT1-VL, Weatherford RPDV-2, Camco/Merla LNM-31R, Camco/Merla WFM-14R

1.5" IPO Gas-Lift Valves

Camco R-20, Weatherford R-2, Camco/Merla N-17R, McMurry Macco C2

1" Gas-Lift Orifices

Camco NOVA, Camco DCR-DK


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Typical VPC Gas-Lift Valve

Performance Plot

Typical VPC Gas-Lift Valve Performance Plot

Camco BK with12/64ths VPCPvoT= 964 Pcf=920 Temp=150



Flowrate-(Mscf/d)

Downstream Pressure - (psig)

0

500

1000

1500

0 200 400 600 800 1000

Camco BK. 1" IPO

VPC Performance Model

Various Port Sizes

No Choke

12/64"

20/64"

16/64"


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How Member Companies

Use VPC Results

For example, in Shell: Only gas-lift valves that have been tested and

modeled by the VPC are recommended for use Any valve found to be inadequate is not recommended

for use

VPC gas-lift valve models have beenimplemented in WinGLUE

They are used in gas-lift design & performance analysis In some cases, valves that have been found to be

inadequate have been redesigned or replace bythe manufacturer This is clearly a win/win for all concerned


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Future Plans of the VPC

In 2001 and beyond, the VPC members haveagreed to:

Continue gas-lift valve testing and modeling Valves/orifices nominated by users

Selected new valves

Several valves of a type/model to check for consistency

Conduct appropriate evaluations Potential for erosion during unloading

Effect of chokes on erosion potential

Potential life cycle of bellows

Impact of various metallurgies


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Other Companies are

Welcome to Join the VPC

The VPC is a "joint industry project." It is funded and controlled by its members

It is not a profit making organization Its purpose is to advance gas-lift performance through

improved gas-lift valve understanding

Any gas-lift operator or service company is welcome

The VPC meets annually, usually in October, to agree onthe budget and plan for the next year

Member companies have found great value in: Having accurate, reliable information on their valves

Having accurate performance models of their valves

Being able to screen out valves that are not satisfactory


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Testing and Modeling

Gas-Lift Valves

Conclusions Most gas-lift wells require gas-lift valves to lift

effectively Valves do not perform as previously assumed

The steady state force balance equation is not sufficient

Thornhill-Craver can not accurately predict gas passage

To effectively design and analyze gas-lift wells,

we must understand gas-lift valve performance API RP 11V2 provides the needed standards

The VPC provides the mechanism to implement thesestandards for the industry

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