Case Study: Intervention-Free, Closed-Chamber Completion Performed in a Highly Deviated Well

eFire-TCP system, CTXR gun release, and 1,200-ft gun string conveyed in a single run allow fullbore access

Challenge: Complete a long section of a highly deviated well in the North Sea, perforating through two casings—one of which has a potential leak—while minimizing rig time required.

Solution: Use the eFire-TCP electronic firing head system for tubing-conveyed perforating deployment along with closed-tubing explosive-actuated release (CTXR) for an intervention-free, closed-chamber completion.

Result: Conveyed a gun string measuring over 1,200 ft, an eFire-TCP firing system, and a CTXR gun release in a single run through the completion.

Complete long, deviated well section through two casings

A major North Sea operator asked Schlumberger to provide a perforating and completion solution in a well whose design limited the use of conventional tubing-conveyed perforating (TCP) or wireline perforating techniques.

The interval to be perforated was highly deviated, over 1,200 ft [365 m] long, and had two liner sizes. The possibility that one of the liners was leaking limited the use of conventional conveyance methods. Further complicating the situation was the operator’s request that the operation, once begun, be completed quickly.

Use eFire-TCP system and CTXR gun release as solution

The length of the interval to be perforated and the high angle of the well required that the guns be tubing-conveyed. Schlumberger proposed using the eFire-TCP electronic firing head system for tubing-conveyed perforating deployment with a CTXR automatic gun release for an interventionfree, closed-chamber completion. The firing heads and automatic gun release would be deployed at the end of the permanent completion along with over 1,200 ft of 2⅞-in, 6-spf, 60° phased guns.

Maintaining pressure within the casing was critical because of the suspected liner leak. The CTXR closed chamber automatic gun release incorporated a biased piston configuration that maintained pressure in the closed system until the gun detonated and also allowed the gun to drop when rathole pressure was higher than pressure inside the casing.

The closed-pipe completion with TCP guns was run in hole and correlated to depth, and the hydraulicset packer and subsea well control equipment were set in place.

The eFire-TCP system, fully controlled from the surface, was immune to pressure spikes or fluctuations, so it allowed pressure testing of the casing and annulus without risk of activating the firing system. When it was time for the guns to be activated, a low-pressure pulse was sent through the production tubing to the eFire-TCP system. After a 20-min delay, the guns were fired.

Immediately upon detonation, the CTXR released the gun string, leaving the well to produce into the tubing string through a fullbore wireline entry guide.

Perform successful, single completion run for fullbore reservoir access

The combined eFire-TCP system and CTXR gun release technologies delivered a system design with the completion flexibility required.

The eFire-TCP system allowed packer-setting and pressure-testing operations to proceed unhindered by the limitations of conventional hydraulic-activated firing heads.

The innovative CTXR autorelease sub maintained tubing integrity where there was the distinct possibility of a liner leak. It also allowed the gun string to be dropped into the deviated rathole just after the guns were detonated, thereby providing fullbore access to the reservoir section.

Download: Intervention-Free, Closed-Chamber Completion Performed in a Highly Deviated Well (0.75 MB PDF)

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