Abstract

ADMA-OPCO had integrity problems in a gas well and abandonment was the only option available to restore the integrity of the offshore multiwell jacket and revive the adjacent wells that had been shut in due to the problems. The integrity problems were oil/gas bubbles observed on the seabed around the conductor pipe and high sustained pressures in the outer cemented casing annuli. The entire jacket was considered very dangerous under these conditions.

Because the leak was determined to be located outside the 18 5/8-in. casing, perforating several intervals was required to improve the chance of a successful squeeze. Some of the intervals were perforated through 3 casing strings and the rest through 4 strings of casing; 7-in., 9 5/8-in., 13 3/8-in. and 18 5/8-in., before being squeeze cemented to cure the problem.

Modeling of the perforating gun performance indicated that penetration through the four casings could be achieved. The modeling was confirmed with laboratory testing in a mock setup to simulate worst case conditions downhole. The laboratory test results were very useful in the final gun selection process. Once the gun and deep penetrating charge type were chosen a local modification was performed to create an 18° phased gun system ideally suited to remedial applications. An optimal cement type was also chosen to be used for this application.

The perforating/squeeze jobs were executed and surface rate and pressure measurements have confirmed that the jobs were successful.

This paper will present the job preparation considerations, the prejob testing of the perforating systems, the local modification used to create the 18° phasing, the cement used for the squeeze and the confirmation that the job was successful. It is believed that this is the first time such an operation has been successfully executed and the results should be of interest to all operating companies.

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