Abstract

A deepwater batch drilling project in north Borneo was planned to produce oil at full potential through water and gas injection wells. The field is located 75 miles offshore in water depths in excess of 3,300 ft. Failure of formation isolation valves (FIV) to open hydraulically in the two injector wells jeopardized future production of the field and compromised the timeline remaining for the semisubmersible to complete its schedule for the rest of the drilling and completion campaign of the producer wells. Attempts to mechanically shift the FIV using slickline were unsuccessful, and the contingency plan of intervention using coiled tubing (CT) was commenced to quickly regain wellbore access.

With the drilling time constraint and the operational limitation of the rig to accommodate CT equipment access, the well intervention campaign was urged to mitigate the FIV problems and save the wells. Tight deck space to perform pressure control rig-up, limited A-frame height to accommodate coiled tubing lift frame (CTLF) operation, and well completion with small restricted clearance that prevents the maximum performance of the downhole tools are the major challenges faced in this project.

A comprehensive job design and planning process was implemented considering the semisubmersible limitations and the restrictions on wellbore access. A fit-for-purpose downhole tool configuration and multiple intervention options were carefully selected to support performing wellbore diagnostics prior to the final decision to mill out an FIV assembly. The CT catenary concept and equipment were applied in the execution stage as a contingency measure to permit curvature bend into the derrick in case the rig heaves risked the A-frame hitting the CT. The overall CT operation was a success and has proven that CT can become a turnkey service in mitigating potential downtime due to completion problems.

This paper discusses the design process and contingency plans that were developed to mitigate the FIV failure where CTLF operation is limited by the completion and surface rig-up in a semisubmersible rig. The lessons learned derived from this case history could be essential in the planning of a deepwater drilling and completion project.

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