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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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Feb. 6, 2001 2001 ASME/API Gas-Lift Workshop 2
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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Feb. 6, 2001 2001 ASME/API Gas-Lift Workshop 3
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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Feb. 6, 2001 2001 ASME/API Gas-Lift Workshop 4
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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Feb. 6, 2001 2001 ASME/API Gas-Lift Workshop 5
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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Feb. 6, 2001 2001 ASME/API Gas-Lift Workshop 6
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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Feb. 6, 2001 2001 ASME/API Gas-Lift Workshop 7
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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Feb. 6, 2001 2001 ASME/API Gas-Lift Workshop 8
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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Feb. 6, 2001 2001 ASME/API Gas-Lift Workshop 9
Typical VPC Gas-Lift Valve
Performance Plot
Typical VPC Gas-Lift Valve Performance Plot
Camco BK with12/64ths VPCPvoT= 964 Pcf=920 Temp=150
Camco BK with16/64ths VPCPvoT= 964 Pcf=920 Temp=150
Camco BK with20/64ths 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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Feb. 6, 2001 2001 ASME/API Gas-Lift Workshop 10
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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Feb. 6, 2001 2001 ASME/API Gas-Lift Workshop 11
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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Feb. 6, 2001 2001 ASME/API Gas-Lift Workshop 12
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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Feb. 6, 2001 2001 ASME/API Gas-Lift Workshop 13
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