Solid expandable tubular patching technique for high-temperature and high-pressure casing damaged wells

Abstract

In view of the issue that casing patching by solid expandable tubular (SET) has a low success ratio in high temperature (HT) thermal recovery wells or high pressure (HP) water injection wells, four key techniques of SET were studied theoretically and experimentally, and the casing patching SET tool for the HT/HP wells was designed. The expandable tubular with post expansion mechanical properties reaching API N80 steel grade was developed. The loading plane angle of expandable connecting thread was optimized as −9°. The sealing piece of inlaid welded copper and the cone coated with tungsten carbide were developed. Based on these researches, a prototype SET patching tool for HT/HP wells has been manufactured. The SET patching tool for HT/HP wells was manufactured. Laboratory experiments demonstrated that the expansion force of the patching tool was between 25 MPa and 32 MPa, the pressure resistance in three periods of alternating temperature load was over 15 MPa, the sealing capacity exceeded 35 MPa, all were up to the designed standard. The field tests in 45 wells in the Liaohe and Tuha oil fields demonstrated that this technique has good adaptability in casing patching in high temperature thermal recovery wells or high pressure water injection wells. After the patching operation, the water pressure 15 MPa was maintained for 30 minutes to test the tool's sealing performance, the pressure drop was less than 0.2 MPa, and the success ratio of one-time construction was 100%. After the casing patching, the oil wells production increase significantly and remarkable economic benefits are achieved. Key words: casing damaged well, thermal recovery, high pressure water injection, patching tool, solid expandable tubular, expansion cone, connecting thread, metal seal, field test