Unless there is support provided by a workover rig or temporary fixed platform, coiled tubing (CT) intervention workover on a small offshore platform is not feasible. Usually, small offshore platforms have low deck load capacity and available deck space is insufficient for CT workover operations. To puzzle out the solution to this issue, CT operations from a vessel were discussed and subsequently developed more than a decade ago. In 2002, the technique was substantially refined and improved to improve safety and reliability, which allows well intervention from the deck of a floating anchored vessel. This technique utilizes a system which provides emergency CT disconnect and effectively compensates wave motion.
The system includes the CT slack-disconnect assembly, reel control cabin, CT stabbing system, platform support gooseneck and a Pan/Tilt/Zoom Closed Circuit video system. The combination of the mentioned equipment allows CT intervention applications to be carried out with minimum equipment on the platform in a safe and secure manner. The system is not only the solution for CT intervention on small offshore platforms but it also saves the rig up/rig down time, therefore minimizing human exposure to equipment handling. The system features improve the overall operation safety and provide an opportunity to perform CT stimulation with large treatment fluid volumes. Fundamentally, this system now forms a key part within an integrated service solution which allows CT services, pumping services, e-line, slick-line and testing services to be performed in a single smooth operation.
In Brunei, this technique has now been taken to a new level. The preferred vessel is now a relatively small self-propelled work boat, similar to those used for rig supply, albeit one fitted with a suitable pedestal crane, capable of lifting an injector head and support frame. These work boats allow swift movement between platforms and reduced reliance on support vessels such as tugs, anchor handlers or supply boats.
This paper introduces the features and benefits of a CT system which is designed to work from the deck of an anchored work boat and briefly summarizes the success of CT intervention campaigns in Brunei since 2007.