Gas Lift Challenges. Gas-Lift Workshop. Qatar February 4-8, Mike Johnson ExxonMobil Production Company

Transcription

1 Gas-Lift Workshop Qatar February 4-8, 2007 Gas Lift Challenges Mike Johnson ExxonMobil Production Company 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).

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 operational organizations 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 Gas-Lift Workshop 2

3 Significant Challenges Operating Gas Lift Challenges Highly deviated, extended reach gas lift wells SPM Pre-loading Dual Gas Lift 2007 Gas-Lift Workshop 3

4 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 7 Production Tubing Build angle 1.5 deg per 20 m, EOB ~ 1624 meters Hold angle 75.2 deg Gas Lift Mandrel w/ orifice 6600 meters, MD casing at 7690 meters, MD 1685 meter, 8.5 horizontal section 7 liner 9375 meters MD, 2613 meters, TVD 2007 Gas-Lift Workshop 4

5 Highly Deviated Extended Reach Wells Challenge: 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 Production Tubing Build angle 1.5 deg per 20 m, EOB ~ 1624 meters Hold angle 75.2 deg Gas Lift Mandrel w/ orifice 6600 meters, MD casing at 7690 meters, MD 1685 meter, 8.5 horizontal section 7 liner 9375 meters MD, 2613 meters, TVD 2007 Gas-Lift Workshop 5

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 Gas-Lift Workshop 6

7 Shop modified KOT for latching bent valve Bent Valve in pocket KOT welded angle extension to reach out and go over bent latch Valve in pocket bent to 40 deg. angle KOT extension designed to straighten latch during jar down operation 2007 Gas-Lift Workshop 7

8 Dual Gas Lift Using High Pressure Gas Lift for single point of injection Definition: Dual gas lift is defined as using gas-lift Shear in Orifice both sides Valve of a failure dual completion Consider with gas running lift supplied a back up mandrel 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. Challenge: Change valve using wireline tractor or coil tubing 2007 Gas-Lift Workshop 8

9 Dual Gas Lift Dual gas lift is most effective if the producing zones are similar in reservoir characteristics. Using High Pressure Gas Lift for single point of injection Experienced difficulties in wells when one producing string is only about % of the other string. Inject at optimum rate Shear Orifice Valve failure Consider running a back up mandrel GOALS Inject in both strings simultaneously Inject as deep possible in both sides. Inject in a stable manner. Challenge: Change valve using wireline tractor or coil tubing CHALLENGES 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. 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. 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. Difficult to achieve and maintain the optimum injection rate to both strings 2007 Gas-Lift Workshop 9

10 Dual Gas Lift Pressure Using High Pressure Gas Lift for single point of injection Shear Orifice Valve failure Consider running a back up mandrel Gas Lift Gradient Depth Flowing Gradient Zone 1 Flowing Gradient Zone 2 Best suited if DP1 is very close to DP 2 Pt 2 DP 2 Pg OP Challenge: Change valve using wireline tractor or coil tubing Pt1 DP 1 Packer Depth Zone 1 Zone Gas-Lift Workshop 10

11 Dual Gas Lift 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. Unloading Valves 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. Operating Valves Unload strings in sequence, lower productive string first Gas-Lift Workshop 11

12 Questions? 2007 Gas-Lift Workshop 12

13 Backup 2007 Gas-Lift Workshop 13

14 Single Gas Lift Performance Zone 1 Zone Gas-Lift Workshop 14

15 Dual Gas Lift Performance Zone 1 Zone 2 Zone Gas-Lift Workshop 15

16 Dual Gas Lift Performance Zone 1 Zone 2 Zone 3 Zone Gas-Lift Workshop 16

17 Dual Gas Lift Performance Zone 1 Zone 2 Zone 3 Zone Gas-Lift Workshop 17

18 Dual Gas Lift Performance 2007 Gas-Lift Workshop 18