?127mm反扣钻杆脱扣失效分析

Analysis on ?127mm Left-hand Drill Pipe Box Connection Thread Deformation Failure

对某油井?127mm反扣钻杆因内螺纹接头胀扣、外螺纹接头拉长变形而导致钻杆脱扣的失效事故进行了调查。通过对钻杆失效接头螺纹宏观、微观分析,并对接头取样进行了理化检验、金相分析。分析结果表明:井下作业过程中,钻杆接头反复上扣,其螺纹部位转矩过大,导致外螺纹被拉长,内径收缩,内螺纹胀大,其螺纹牙相互挤压剪切,导致钻杆接头连接强度降低而滑脱。

In an oil Wells,A ？127mm left-hand drilling pipes accident was investigated for the reason of left-hand drilling pin/box connection thread deformation and lead to the failure of drill pipe tripping accidents.Through analyzing the macro/micro drill pipe failure joint thread,and the joint sampling for the physical and chemical inspection and analysis of metallographic.Analysis results show that,during the downhole operation process,the tool joint buckled repeatedly,the thread parts,excessive torque caused pin elongated,diameter shrinkage,internal thread swell,and the thread mutual extrusion shear,results in the decrease of strength of drill pipe joint connection and slippage.