Challenges and Solutions of Concentric Coiled Tubing Fishing

Abstract

Concentric coiled tubing technology has many applications for well intervention activities ranging from wellbore cleanout to well unloading and delivering multiple chemicals downhole via separate conduits. Technology historically developed for ultra low bottom hole pressure applications but currently utilization of it was expanded to wellbores with positive wellhead pressure. Concentric Coiled tubing string present similar risk and challenges as Conventional CT. Stuck in hole situation is one of the most notorious situations that requires very close attention and detailed contingency recovery planning. Unlike single pipe recovery where industry has very well-established guidelines and expertise, concentric pipe technology historically lacked both detailed planning and recovery experience. This paper details out the engineering design to address recovery of the CCT. Paper highlights stages requiring for the successful project delivery, step by step guideline and lists out purpose build equipment. Although proposed engineering solutions was not implemented due to the contingency nature, nevertheless careful approach and detailed engineering, risk assessment methods used in developing precise guidelines provides very good resource into existing industry challenge.