1. 2001 ASME/API Gas-Lift Workshop
Testing and Modeling Gas-Lift Valves by
Cleon Dunham, Oilfield Automation Consulting
Ken Decker, Decker Technology
November 12, 2001
2001 Fall 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
November 12, 2001
2001 Fall 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)
November 12, 2001
2001 Fall 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 dynamic operation
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 these standards on a routine basis
November 12, 2001
2001 Fall ASME/API Gas-Lift Workshop

5. Gas-Lift Valve Performance Clearinghouse (VPC)
VPC formed in 1996 as JIP (joint industry project) 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 or model is tested
November 12, 2001
2001 Fall ASME/API Gas-Lift Workshop

6. Gas-Lift Valve Performance Clearinghouse (VPC)
Based on these tests, the VPC develops accurate 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
November 12, 2001
2001 Fall 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
Exxon Shell International
Shell International Weatherford
Weatherford
November 12, 2001
2001 Fall 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 Valves
Camco BKF-6, Camco BKR-5, Camco SRF-10, Camco BKF-12, McMurry Macco RF-1, Weatherford RF-1BL, Weatherford RFX-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
Altec AT1-0, Camco NOVA, Camco DCR-DK
November 12, 2001
2001 Fall ASME/API Gas-Lift Workshop

9. Typical VPC Gas-Lift Valve Performance Plot
Camco BK. 1" IPO
VPC Performance Model
Various Port Sizes
No Choke
20/64"
16/64"
12/64"
November 12, 2001
2001 Fall ASME/API Gas-Lift Workshop

10. How Member Companies Use VPC Results
For example, in at least one member company:
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 been implemented 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 by the manufacturer
This is clearly a win/win for all concerned
November 12, 2001
2001 Fall ASME/API Gas-Lift Workshop

11. 2001 Fall ASME/API Gas-Lift Workshop
Future Plans of the VPC
In 2001 and beyond, the VPC members have agreed 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
November 12, 2001
2001 Fall 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 February or October, to agree on the 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
November 12, 2001
2001 Fall 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 these standards for the industry
November 12, 2001
2001 Fall ASME/API Gas-Lift Workshop