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Gas-Lift WorkshopQatar
February 4 - 8, 2007
This presentation is the property of the author(s) and his/her/their company(ies).It may not be used for any purpose other than viewing by Workshop attendees without the expressed written permission of the author(s).
Gas Lift Challenges Mike JohnsonExxonMobil Production Company
Feb. 4 - 8, 2007 2007 Gas-Lift Workshop 2
Corporate Separateness
Exxon Mobil Corporation has numerous subsidiaries, many with names that include ExxonMobil, Exxon, Esso and Mobil. For convenience and simplicity in this presentation, the parent company and its subsidiaries may be referenced separately or collectively as "ExxonMobil."
Abbreviated references describing global or regional operationalorganizations and global or regional business lines are also sometimes used for convenience and simplicity.
Nothing in this presentation is intended to override the corporate separateness of these separate legal entities. Working relationships discussed in this presentation do not necessarily represent a reporting connection, but may reflect a functional guidance, stewardship, or service relationship.
Feb. 4 - 8, 2007 2007 Gas-Lift Workshop 3
Significant Challenges Operating Gas Lift
Challenges• Highly deviated, extended reach gas lift wells• SPM Pre-loading• Dual Gas Lift
Feb. 4 - 8, 2007 2007 Gas-Lift Workshop 4
Gas Lift Mandrel w/ orifice valve @ 6600
meters, MD
Build angle 1.5 deg per 20 m, EOB ~ 1624 meters Hold angle 75.2 deg
7” liner 9375 meters MD, 2613 meters, TVD
7” Production Tubing
1685 meter, 8.5” horizontal section 9.625” casing at 7690 meters, MD
Highly Deviated Extended Reach Wells
• Using high pressure gas lift for deep single point of injection
• Have begun running a shallower back up mandrel with a dummy for unloading wells
Feb. 4 - 8, 2007 2007 Gas-Lift Workshop 5
Gas Lift Mandrel w/ orifice valve @ 6600
meters, MD
Build angle 1.5 deg per 20 m, EOB ~ 1624 meters Hold angle 75.2 deg
7” liner 9375 meters MD, 2613 meters, TVD
7” Production Tubing
1685 meter, 8.5” horizontal section 9.625” casing at 7690 meters, MD
Highly Deviated Extended Reach WellsChallenge: Change valve using wireline tractor or coil tubing•Positive surface indications of valve setting in pocket
•Maximum KOT and valve latch/body tolerances for push – pull forces
•KOT design to assure valve/pocket alignment for setting valve at horizontal angle with pocket on the high side of the tubing.
•Industry experience using CT in horizontal section – SPE Paper 60722
Feb. 4 - 8, 2007 2007 Gas-Lift Workshop 6
Preloading of Side Pocket Mandrels
•Reoccurring problems with difficulty or inability to retrieve dummies and valves from side pocket mandrels. Latches and valves may be bent or broken off during wireline operations.
•Some equipment may be installed at the rig location rather than in a shop.
•No common or recommended procedure within the industry to insert the device into the pocket in the shop prior to running in the well.
•Where feasible, we have begun running more live valve strings on initial completion to reduce number of wireline jobs required to place well on gas lift.
•We need an industry “Best Practice” for pre-loading side pocket mandrels.
Feb. 4 - 8, 2007 2007 Gas-Lift Workshop 7
Shop modified KOT for latching bent valve
Valve in pocket bent to 40 deg. angle
Bent Valve in pocket
KOT welded angle extension to “reach
out” and go over bent latch
KOT extension designed to
straighten latch during jar down
operation
Feb. 4 - 8, 2007 2007 Gas-Lift Workshop 8
Dual Gas Lift•Using High Pressure Gas Lift for single point of injection
•Shear Orifice Valve failure
•Consider running a back up mandrel
Challenge: Change valve using wireline tractor or coil tubing
Definition: Dual gas lift is defined as using gas-lift in both sides of a dual completion with gas lift supplied through same tubing-casing annulus.
Does not include:
If one side is flowing naturally and not equipped with gas lift valves.
If one side is not a liquid producer (eg: water injector, gas injector, gas producer).
If one side uses macaroni string for gas lifting.
Feb. 4 - 8, 2007 2007 Gas-Lift Workshop 9
Dual Gas Lift•Using High Pressure Gas Lift for single point of injection
•Shear Orifice Valve failure
•Consider running a back up mandrel
Challenge: Change valve using wireline tractor or coil tubing
Dual gas lift is most effective if the producing zones are similar in reservoir characteristics. Experienced difficulties in wells when one producing string is only about 10 –15 % of the other string.
Difficult to achieve and maintain the optimum injection rate to both strings
• Inject at optimum rate
Severe production heading or fluctuations that may be caused by unsteady or fluctuating injection at the downhole operating point can lead to significant inefficiency in gas lift operation.
• Inject in a stable manner.
•Lower producing zones always suffer as top packer needs to be set above the top zone. Hence, the deepest mandrel is still too far from the zones.•Use of insert string can improve the injection point in the lower zone.
• Inject as deep possible in both sides.
•Very often one side “robs” all the gas.•Low PI zones have very low flowing tubing pressure with large, casing and tubing pressure differential, causing gas to go to this string.•Use of small port size valve helps this problem but not eliminated totally.
• Inject in both strings simultaneously
CHALLENGESGOALS
Feb. 4 - 8, 2007 2007 Gas-Lift Workshop 10
Dual Gas Lift
•Using High Pressure Gas Lift for single point of injection
•Shear Orifice Valve failure
•Consider running a back up mandrel
Challenge: Change valve using wireline tractor or coil tubing
Pressure
Dep
th
Gas LiftGradient
Pt1
Pt 2
Zone 1
Zone 2
Pg OP
FlowingGradientZone 2
FlowingGradientZone 1
Best suited if DP1 is very close to DP 2
DP 2
DP 1 Packer Depth
Feb. 4 - 8, 2007 2007 Gas-Lift Workshop 11
UnloadingValves
OperatingValves
Gas Lift Design Practices (trial and error process)
Production Pressure Operated Valves (PPO) as unloading valves and Injection Pressure Operated (IPO) as operating valve.
IPO operating valve allows for higher gas injection rates compared to PPO valve
Valve closure preserves casing pressure during shut downs.
Mandrel Spacing PPO valve mandrel spacing design
spacing for both strings accommodates either IPO or PPO valve spacing intervals
Space both strings such that either can unload the packer fluid from the well.
Unload strings in sequence, lower productive string first.
Dual Gas Lift
Feb. 4 - 8, 2007 2007 Gas-Lift Workshop 12
Questions?
Feb. 4 - 8, 2007 2007 Gas-Lift Workshop 13
Backup
Feb. 4 - 8, 2007 2007 Gas-Lift Workshop 14
Single Gas Lift Performance
Zone 1
Zone 2
Feb. 4 - 8, 2007 2007 Gas-Lift Workshop 15
Dual Gas Lift Performance
Zone 1
Zone 2
Zone 3
Feb. 4 - 8, 2007 2007 Gas-Lift Workshop 16
Dual Gas Lift Performance
Zone 1
Zone 2
Zone 3
Zone 4
Feb. 4 - 8, 2007 2007 Gas-Lift Workshop 17
Dual Gas Lift Performance
Zone 1
Zone 2
Zone 3
Zone 4
Feb. 4 - 8, 2007 2007 Gas-Lift Workshop 18
Dual Gas Lift Performance