通过钻杆刺缝宏观形貌、断口微观形貌观察及EDS谱分析, 结合钻杆材料的力学性能、化学成分和显微组织分析, 对尺寸为φ127 mm×9.19 mm的G105钢级钻杆管体的刺漏原因进行了分析。结果表明: 该钻杆刺漏属于早期腐蚀疲劳开裂; 钻杆外壁表面受到井下弱酸性液体的腐蚀而存在多个腐蚀坑, 腐蚀坑底部易产生应力集中, 在交变应力的作用下, 多条裂纹分别在腐蚀坑底快速萌生; 钻柱在钻进的过程中存在跳钻及钻柱组合结构中严重的截面突变, 加速了该钻杆疲劳裂纹的扩展; 这些疲劳裂纹不断扩展, 当其中一条裂纹穿透管壁时, 钻杆便发生刺漏。

Through the examination of macroscopic morphology of cracks on a drill pipe and microscopic morphology of its fracture, EDS analysis, mechanical property test, chemical composition and microstructure analysis, the washout reasons of the drill pipe with φ127 mm×9.19 mm in size made of G105 steel were analyzed. The results show that the washout of the drill pipe was ascribed to early corrosion fatigue. There were some corrosion pits on the outer wall of the drill pipe body due to the corrosion of weak acid fluid in downhole, which caused stress concentration at the bottom of corrosion pits. Under the action of alternating stress, multiple cracks quickly initiated at the bottom of corrosion pits. The bit jumping during drilling process and serious cross-section mutation of combined drill stem structure accelerated the expansion of fatigue cracks in the drill pipe. When one of the cracks penetrated the pipe wall, washout happened in the drill pipe.