Schlumberger

Case Study: Unique Perforating Solution for Chevron Jack Well

True 25,000-psi perforating system based on proven technology and track record

Challenge: Chevron needed to perforate the large-casing (10 1/8-in) Jack well in 7,000 ft of water, more than 20,000 ft under the sea floor with bottomhole pressure of approximately 19,500 psi, using reliable, qualified equipment.

Solution: Getting a string down to the required depth meant back-engineering the tools based on casing size and pressure conditions. The Schlumberger team created a unique combination of tools that functioned together as a true 25,000-psi perforating system: 7-in, 18 spf, 25,000 psi rated gun; 25,000 psi rated SXVA perforating shock absorber; and 25,000 psi rated redundant eFire electronic firing head system.

Result: The Jack well was successfully perforated and tested, achieving all of the targeted objectives. Schlumberger has been recognized as the supplier of choice for deepwater perforating systems.

Extreme depth, low permeability

Chevron announced discovery of the Jack prospect in September 2004. It is approximately 270 mi southwest of New Orleans and 175 mi offshore. Chevron needed to successfully perforate a large-casing (10 1/8-in) well with bottomhole pressure at approximately 134 MPa [19,500 psi] with reliable and qualified equipment. The target was a Wilcox 1 sand body with 274 m [900 ft] gross oil sand. The length of the interval, combined with the interval depth, presented a substantial challenge. Considering the depth and low permeability, a long-term drillstem testing evaluation was required to determine if future field development was commercially feasible.

For Chevron, coming to Schlumberger first for a solution was a natural choice based on their shared prior positive experience working on the Tahiti well in 2004. The Schlumberger team was able to fully qualify all the required tools under the Jack well’s specific downhole conditions more quickly than the planned operation required. Chevron was an active part of the process in defining the specifications and scope of the project.

True 25,000-psi perforating system

Back-engineering the tools based on casing size and pressure conditions was necessary to get a string down to the required depth. The Schlumberger team created a unique combination of tools functioning together as a true 172-MPa [25,000-psi] perforating system: a 7-in, 18 spf, 25,000 psi rated gun; the 25,000 psi rated SXVA perforating shock absorber; and the 25,000 psi rated redundant eFire electronic firing head system.

All components of the system are based on proven technology and track record. The engineering, manufacturing, and testing took approximately 9 months to achieve full qualification. At the Schlumberger Reservoir Completions (SRC) Center in Rosharon, Texas, tests using the perforating system were conducted. The SRC facility was uniquely equipped to confirm the efficacy and safety of the perforating system at this pressure and depth.

Additional tests at SRC on the IRIS Intelligent Remote Implementation System dual valve were run for 90 d in a test vessel that completely replicated the Jack well’s downhole conditions. The IRIS dual valve was used as a well control tool and managed putting the underbalance in place for the Jack well.

The perforating gun was originally developed for the Tahiti well and is qualified to even higher pressures. It has an area open to flow (AOF) of more than 18 in²/ft. The SXVA shock absorber suppresses shock during the detonation of large guns and is required with all 7-in guns. The eFire system uses a specialized low pressure pulse command, has a precise time delay, and reduces risk further by using no primary high explosives. Multiple safety barriers and the ability to abort the firing command provide a high level of safety. The eFire firing system produces lower pressure exposure for the guns.

Safety and environmental protection were both emphasized as priorities during the Jack well test. The team achieved a record of no incidents involving days away from work and no spills. All excess fluids were delivered to a barge for proper disposal and no oil was burned.

Current success, future plans

The Jack well was tested in 2,134 m [7,000 ft] of water, more than 6,096 m [20,000 ft] under the sea floor, breaking the 2004 Tahiti discovery well record as the deepest successful well test in the Gulf of Mexico. After this success, Chevron committed to future use of the high pressure perforating gun system developed for the Jack well, and also asked Schlumberger to develop a 4.72-in, 21 spf, 172 MPa [25,000 psi] gun system for multiple future field developments in the deepwater Gulf of Mexico.


Download: Unique Perforating Solution for Chevron Jack Well (0.09 MB PDF)

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Case Study: True 25,000-psi perforating system based on proven technology and track record
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