A Pioneer Step in Restoring Well Integrity for Workover Rig Intervention Through Instrumented Coiled Tubing and Through-Tubing Inflatable Packer

Abstract

Abstract Even though technology development has leveraged a consistent growth in the number of rigless interventions, many remedial programs still require the support of workover rigs. In southeast Kuwait, mechanical constraints at the production tree tubing hanger prevented the operator from installing the blowout preventer (BOP) of the workover rig following the conventional practices and called for a custom-fit approach to enable the required number of pressure barriers to intervene this well. The intervention approach relies on instrumented coiled tubing (CT) for well killing and temporary well suspension. CT real-time downhole telemetry enables accurate placement and setting of a through-tubing inflatable and retrievable packer (TTIRP) inside the production tubing. Once the packer integrity is pressure tested in both directions, the CT is disconnected, and then a sand plug followed by an acid soluble cement plug are spotted on top of the TTIRP. Upon confirmation of cement plug integrity, the workover rigs come into play to nipple down the production tree and install the BOP. Instrumented CT is then rigged up and run back-in-hole to dissolve the cement plug, circulate the sand out, and recover the TTIRP to surface. The candidate well where this innovative intervention workflow was implemented had a maximum potential wellhead pressure in the order of 1,100 psi and a plugback true depth (PBTD) near 5,000 ft. The well was completed with 3 1/2-in. production tubing set close to 3,500 ft MD and 8 5/8-in. casing to PBTD. An e-line through-tubing puncher was carried out in the production tubing before the first CT run to enable circulation of killing fluid. TTIRP setting depth was conditioned via instrumented CT and a high-pressure rotary jetting tool, and displacing the wellbore to brine, resulting in a shut-in wellhead pressure near zero psi. In the next CT run, TTIRP was positioned around 620 ft, and important steps like depth correlation, packer inflation, and packer anchoring tests were actively monitored using real-time downhole measurements. Both positive and extended inflow tests using live downhole pressure monitoring were carried out to confirm the effectiveness of the TTIRP sealing before the CT was disconnected from the packer assembly. Once the TTIRP was released, the temporary suspension was completed following the methodology described above. Finally, the well was closely observed at surface with zero pressure for more than 24 hours, receiving acceptance from the operator to service the well. Upon completion of the workover program, the estimated saving by eliminating deferred production was estimated to be around 200,000 bbl. This case study from southeast Kuwait discusses a custom-fit approach via instrumented CT and TTIRP for restoring well integrity in wells planned for workover rig intervention where mechanical constraints at production tree prevented installing the workover rig BOP, and the lessons learned are now a reference for operators in the Middle East with wells with similar challenges.