Successful Control of High-Pressure Gas Well by Use of a Crosslinked Gel During Coiled-Tubing Fishing

Abstract

Summary Good well- and reservoir-management practices demand that new gas wells be tested to expected potentials at the onset of production and buildup surveys be conducted at specified intervals during the life of the well. This will help to determine the deliverability of the wells, obtain base reservoir parameters, and improve reservoir surveillance in monitoring abandonment conditions. It was the pursuit of these data gatherings that lead to the multirate buildup survey that resulted in stuck temperature and pressure memory gauges at RN® No-Go nipple. The gas-production capability of this well was estimated at 150 MMscf/D. After the installation of the memory gauges, multirate and 10-hour buildup tests were conducted. During the retrieval of the bottomhole-pressure (BHP) gauges, several incidents led to three fish getting stuck successively in the wellbore. The operator was faced with many options, each with a limitation: Continue the well in an unsafe manner at 50% potential, attempt a workover, or attempt a coiled-tubing (CT) rigless intervention. During the planning stage of the remedial operation, success in retrieving the multiple fish was identified to be dependent upon the ability to kill the high-pressure gas well with a time-dependent and acid-degradable crosslinked-gel system with a high-rate bullhead pumping technique and appropriate wireline/CT fishing tools. These tools would locate and grab the wire rope simultaneously, minimizing run time in a cost-effective manner. The kill fluid needed to have low damage potential to the formation and be capable of preventing the migration and fingering of formation gas to the surface throughout the fishing operation, which lasted approximately 1 month. Key success was identified in the ability of the CT to compress the wire rope in bunches and withstand the extra overpull required to free the stuck fish. At the end of the operation, in which some challenges were encountered, five stuck fish (two additional fish became stuck during the attempt to free the first three) were retrieved successfully and prefishing conduit potential was retained, thus indicating that the crosslinked gel degraded completely at the end of the fishing operation, leaving the near-wellbore region undamaged. The gain from the operation includes leaving the formation in an undamaged state, cost savings, high net present value, and meeting the gas-supply obligation. More than USD 2.0 million was saved operationally with the choice of rigless activity when compared to the rig re-entry alternative. The well is still producing satisfactorily 5 years after this activity. This paper presents the engineering design and field application of, as well as lessons learned from, fishing operations.