Abstract
A certain Field development is located offshore Malaysia in 60 meters of water. Well B-10 was drilled in 1991 with deviations up to 69° and was completed as a dual string producer from sands E-12/13 in the short string and E-14 in the long string via two strings of 2-7/8" tubing in 9-5/8" 40 lbs/ft casing. In 2008, the E-14 sand was no longer productive with a water cut of 95% and so a water shut-off initiative was performed using a coiled tubing cement squeeze. The job resulted in failure probably due to the less than expected rate of cement fluid loss into the formation resulting in its unintentionally plugging the casing and tubing and blocking access to the formation for reperforating.
To regain access to the casing and the E-14 sand, it was necessary to perform two procedures with coiled tubing (CT); to mill the cement in the tubing and to underream the 9-5/8" casing thru the 2-7/8" tubing. The extended reach required to clean the tubular down to the casing wall posed a major challenge with the possibility of getting the underreamer stuck in the tailpipe, being unable to retract it to re-enter the tubing or damaging the tubing and/or the completion equipment during retrieval. The milling and under-reaming job were successfully carried out despite the challenges, including milling cement in the 9-5/8" casing, high 69°deviation, high tool expansion requirement from 2-7/8" tubing to 9-5/8" casing and the use of nitrogen as a motor drive fluid.
In this paper the authors will review the history of the well and the problems that lead to the cement job being performed, the reasons for the subsequent problems and the consequences of failure. Subsequently, the paper will review in detail the risks involved in the proposed procedure and the new technology offered. The paper will also discuss the cleanout procedure which was performed successfully and re-established full bore access to the perforations.
