某G105钻杆管体刺穿失效原因分析

Causes Analysis of a G105 Drill Pipe Body Piecing Failure

针对某井G105钻杆管体刺穿失效问题,通过化学成分分析、力学性能测试、金相检测、扫描电镜(SEM)等手段,对该失效钻杆管体刺穿失效原因进行综合分析。结果表明,钻杆管体刺穿的主要原因是在交变载荷作用和Cl-作用下,钻杆外表面腐蚀坑底的裂纹萌生并加速扩展,当裂纹扩展穿透整个壁厚时,高压钻井液从内孔刺出,形成冲蚀,导致管体刺穿失效。最后指出,应加强对同批钻杆的无损探伤检验,避免带腐蚀疲劳微裂纹的钻杆下井使用。

Aiming at the problem of piercing failure of G105 drill pipe body in a well,the causes of piercing failure of G105 drill pipe were analyzed by means of the chemical composition analysis,mechanical property test,metallographic examination and scanning electron microscope(SEM).The results show that the main reason of drill pipe piercing is the crack initiation and accelerated propagation of corrosion pit bottom on the outer surface of drill pipe under the alternating load and Cl-.When the crack propagates through the whole wall thickness,the high-pressure drilling fluid will pierce out of the inner hole and form erosion,leading to the failure of pipe piercing.Finally,it is pointed out that the nondestructive testing of the same batch of drill pipes should be strengthened to avoid the drill pipes with corrosion fatigue microcracks.