First-Time Application of Catenary Concentric Coiled Tubing and Vacuuming Technology

Abstract

An operator needed to perform wellbore intervention on four low-bottomhole-pressure offshore wells in Malaysia. High sand production was consistent in all the wells, precluding access to the producing zones in the lower completion. The wells had been shut in since 2011, and previous cleanouts using conventional coiled tubing (CT) and nitrogen had been unsuccessful. The job had to be performed from a work barge in a catenary style, meaning that the injector head, blowout preventers, and power pack were on the platform, but all were operated from a barge. The advanced wireless catenary unit made it possible to complete the operation with only the CT and three flexible lines connecting the barge and the vessel. Due to the nature of the concentric coiled tubing (CCT)—designed to flow returns back to surface—all returns had to be routed away from the platform and onto the barge. After an analysis and planning session, the operator and the service provider decided to use a CCT cleanout system with a switchable jet-pump designed to remove solids and liquids from ultralow pressure wellbores that are not treatable with standard circulating methods. The operational plan also called for building a specialized CT connector that would enable conventional operations, such as fishing and sleeve manipulation with CCT. This was the first time that vacuuming technology and catenary CCT were used together to perform a cleanout operation. The results were impressive as extensive amount of sand was removed from the wellbores to surpass target production by 185%. This paper will focus on a campaign in the South Furious field of Sabah, Malaysia in which both the logistic and operational challenges were successfully overcome with 112 days of incident free operations.