Sand cleanouts remain one of the most common applications of coiled tubing (CT) in the oil and gas industry. However, offshore operational complexity increases with deck space limitations, lower crane capacity and low reservoir pressures. This paper reviews one such challenging offshore scenario, with limited spatial capacity and not space for a full CT fleet. The paper describes the challenges encountered and the solutions formulized to conduct a successful concentric CT boat spooling and intervention.
The first operational task of boat spooling was completed from an offshore vessel to the platform using two injectors, one on the vessel and the other on the platform. The need for boat spooling arose due to the limited lifting capacity at the platform which was below the weight of the concentric coiled tubing (CCT), 1-in. CT constrained in a 2-in. string. At project end, the CCT was removed in a similar manner. Deck space was also limited and the fluid and nitrogen support equipment (pumps, tanks, chemical mixing) were located on a supply vessel.
Numerous challenges were faced during the operation, all of which were successfully tackled without health, safety or environmental (HSE) incident. Additionally, there was a provision of tanks and pumps on the platform to act as a back-up in the event of failure of supply from the vessel to the CT. This paper describes the methods utilized to successfully boat spool 14,825-ft of pipe of total weight 27-tonnes and cascade the benefits to future boat spooling operations throughout the globe.
While catenary CT operations are common in the Asia Pacific, boat spooling remains a relatively rare operation in the industry. It is believed this is a first operation where a CT operation was conducted in this manner with the fluid and nitrogen pump on a supply vessel and boat spooling was conducted for CCT. Detailing the execution procedures, risk mitigations, operational results and lessons learning will be of value to the industry.