Pushing the Limits of Coiled Tubing Intervention in Mega-Reach Wells: A Success Story Offshore India

Abstract

Abstract Coiled Tubing (CT) operating envelopes have become challenged by the increasing length of lateral sections in extended-reach wells. CT was deployed in a 3800 mMD, mega-reach, offshore well with a 2600 m lateral section and a Measured Depth (MD): Total Vertical Depth (TVD) ratio of 3.2 to perform fishing and sliding sleeve manipulation jobs. Customized CT intervention solutions designed to perform these job objectives are presented in this paper. A tailor-made hourglass-type 1.75 in CT string was designed since the weight limitations of the rig crane prevented the possibility of lifting 2 in CT onto the platform. A customized Bottom Hole Assembly (BHA) with self-centralizing components and an Extended Reach Tool (ERT) was used to improve CT reach while maintaining the ability to pass through shouldered profiles in the completion jewelry. Laboratory tests on various lubricants yielded a suitable metal-to-metal Friction Reducer (FR) to use while running the CT to reduce drag, prevent lock-up, and further improve CT reach in the well. The first objective of the CT intervention was to retrieve a wireline tractor stuck between two gas lift valves. The fishing BHA comprised a mechanical JDC type pulling tool and a customized bell guide to engage the top of the fish. A hydraulically activated downward impact tool with an ERT was included in the BHA to improve the achievable set-down weight at the target depth and increase the likelihood of engaging the fish. The fish was then successfully retrieved in under 24 hours. Once retrieved, sliding sleeves in the lower completion were now accessible for CT-based manipulation. The sleeve manipulation BHA comprised a mechanical BO type shifting tool with an ERT to perform selective profile manipulation. FR was pumped along the heel section of the wellbore to achieve a friction coefficient reduction of nearly 30%, which improved CT reach and maximum set-down at the BHA. The operation was complete once the sleeve manipulation was performed successfully and the well was put on production. CT intervention in Extended-Reach (ER) wells is technically challenging and operationally complex. Furthermore, available literature and case histories on this topic are sparse. This paper presents key learnings from both the planning and execution stages that made this challenging job successful. It aims to serve as a reference for operators and service companies to plan, develop, and execute similar CT well intervention solutions.