Cement Packer: Recovery of Bypassed Reserves in Highly Deviated Well Using Large-Volume Cement Through Coiled Tubing, Offshore Niger Delta

Abstract

Recently, a multinational exploration and production (E&P) company identified an opportunity for production optimization in a shallow reservoir with the zone of interest behind casing and without using any form of isolation for completions. A major challenge during this operation was the engineering design, as this was the first time a catenary cement operation of more than 31.8 m3 (200 bbl) of slurry would be pumped through coiled tubing (CT), in addition to the high well deviation (~79°) consideration for installation of the cement retainer. Additionally, insufficient deck space on the platform and load-bearing capacity to accommodate the intervention spread presented a potential derailer for the attic oil development. A rigless well intervention program was designed using a 1.75-in. (125K) CT catenary system unit, which could be installed on a barge. The system would allow better CT reach and a higher injector snub/pull capacity. CT was used to install the cement retainer, punch holes in the 4 1/2-in. tubing, and pump cement. A total of 34.6 m3 (218 bbl) of 15.8-lbm/gal resilient slurry was pumped through CT, which was equivalent to pumping a cement volume approximately six times greater than the CT volume. This was necessary to place a 1056-m cement packer in the 4 1/2-in. tubing 9 5/8-in. casing annulus and place 200 m of cement on the cement retainer. The operation was successfully completed using CT, avoiding more costly rig options for recompletion of the well. Zonal isolation was achieved, and the bypassed reservoir pay was perforated with ~600 B/D production. This approach proved to be cost-effective, with savings of approximately USD 1.3 million, which was achieved without compromising operational and safety performance. Rigless recompletion has been a cost-effective approach for production optimization in mature fields. However, existing well architecture, access to bypassed hydrocarbon pays, and environmental characteristics present challenges for developing some of these reserves.