Subsea Well Plug and Abandon Intervention Using a Coiled Tubing Conveyed Inflatable Packer A Case Study

Abstract

Failing to properly abandon a well can create significant safety and environmental hazards, lead to noncompliant status with regulatory agencies, and harm the operator's image. This case study follows the plug and abandon interventions of five subsea wells located offshore East Kalimantan, Indonesia that had been left shut in since the 1980s after they stop producing. The questionable well integrity and limited circulation paths of these older subsea wells had the potential to generate additional hazards unless properly addressed. An inflatable packer run on coiled tubing (CT) was chosen to address the challenge of well integrity because the packer was able to isolate the upper completion and subsea tree while cement was being injected into the reservoir. Hence, exposure of the well components to pressure was minimized, which consequently minimized the risk of having a well control issue due to overpressure. Another challenge stemmed from the difficulties of placing cement in the casing–production-tubing annulus as the return line on the annulus side was removed due to corrosion. A CT-conveyed inflatable packer set in between two punch holes on production tubing allowed for accurate cement placement in the casing–production-tubing annulus. The operation was successfully performed. The reservoir in each of the five wells was safely plugged with cement and the inflatable packers were left in hole as additional barriers. Every cement plug placed in the wells was tested to 1,000 psi to prove the integrity of both the cement and the packer. The ability to place cement in the annulus ensured full coverage of the wellbore without the need to cut and retrieve production tubing. Inflatable packers allowed cement to be pumped down through CT to the annulus through the lower punch hole, and the return to go back to the surface through upper punch holes and up through the production tubing. Twenty inflatable packers were deployed in five wells for both purposes mentioned above, thus proving the reliability of the inflatable packer application in this type of intervention.