Successful Control of High-Pressured Gas Well Using a Crosslinked Gel during Coiled-Tubing Fishing

Abstract

Abstract Good well and reservoir management practices demand that new gas wells be tested to expected potentials at the onset of production and build up surveys carried out at specified intervals during the life of the well. This will help to determine the deliverability of the wells, obtain base reservoir parameters and for reservoir surveillance in monitoring depletion of gas reservoirs. It was in pursuit of the above data gathering that lead to the stalled Multi-rate Build Up survey resulting to stocked temperature and pressure memory gauges at RN-nipple. The production capability of this well was estimated at 150 MMscf/d of gas. Following the installation of the memory gauges, Multi-rate and 10-hour Build-Up tests were conducted. During the retrieval of the BHP gauges, several incidents lead to three successive fishes getting stocked into the well bore. The Operator was faced with many challenges: ‘do nothing and produce the well in an unsafe manner at 50% potential’, ‘attempt a work over’ or ‘attempt a coiled tubing rigless intervention’, with each option having its attendant limitations. During the planning stage of the remedial operation, success in retrieving the multiple fishes was identified to come from the ability to kill the high pressure gas well with a time dependent and acid degradable cross-linked gel system through a high rate bullhead pumping technique and appropriate wireline/coiled tubing fishing tools that will simultaneously locate the wire rope and grab it, minimizing run-time in costs effective manner. The kill fluid had low damage potential to the formation was capable of preventing the migration and fingering of formation gas to the surface throughout the fishing operation that lasted for approximately one month of 24-hour day. Key success was also identified to be the ability of coiled tubing to compress wire rope in bunches and exertion of extra over pull to aid in freeing the stuck fish. At the end of the operation that lasted for one month with difficult challenges; the five (3+2) stuck fishes were successfully retrieved and pre-fishing conduit potential was retained, indicating that the cross-linked gel completely got degraded internally at the end of the fishing operation leaving the near wellbore region undamaged. The gain from the operation includes leaving the formation in undamaged state after the operation, cost savings, high NPV and escaping from penalty for failing to meet gas contractual obligation if the well is produced at less than programmed production. Over $2.0 million was saved operationally with the choice of rigless activity when compared to other alternatives and the well is still producing satisfactorily after more than five years from the time of this activity. This paper presents the engineering design, field application and learning from the fishing operations.