苛酷な坑井条件下における油井管ねじ継手の使用性能とその最適メークアップ方法

Abstract

With hostile drilling environment, multi-performance has been required for tubular connections in addition to conventional performance, so premium connection with metal-to-metal seal has become popular. This paper deals with the performance properties of tubular connections used in typical oil and gas wells, and describes the appropriate make-up operation and the torque resistance of the connections.The make-up torque was measured in the laboratory under the simulated field operations. The connection performance was evaluated using the full-size combined loading tester under the simulated conditions of hostile wells such as horizontal wells, sour service wells, and steam injection wells.As for the results of the test, the make-up torque increases when the grease quantity is small and the temperature is low. In wells, the torque resistance of the connection improves under axial loading, pressurizing, and bending. The joint strength of Round connection is lowered by bending, though that of Buttress and premium connection is not degraded. However, the joint strength decreases in direct proportion to the wear area ratio of the pipe body. Bending moment is not more detrimental to sealing integrity than the axial loading. In sour service wells, there are some possibilities of SSC occurrence at the coupling, so the casing design is required to control the hoop stress on the coupling less than the threshold stress. In steam injection wells, the casing pipe is deformed by the excessive axial load due to the thermal expansion and only the premium connection can maintain the gas tightness.In conclusion, the make-up torque can be stabilized by solving the effects of operation factors, and the connection performance described in this paper may be effective for planning a more economical and reliable casing design in oil wells. Dope of the sufficient compound grease, avoidance of the low temperature make-up, and usage of the weight compensator are recommended to avert some make-up troubles.