川渝地区某气井钻铤发生断裂事故，通过宏观分析、扫描电镜分析、金相检验、化学成分分析和力学性能试验等方法，结合现场服役情况，对钻铤的断裂原因进行了分析。结果表明：钻铤断裂类型为腐蚀疲劳断裂，主要原因为钻铤主台肩面密封不良，导致钻井液冲蚀台肩面和外螺纹根部，形成腐蚀坑，在钻铤旋转钻进时，受到循环应力与腐蚀共同作用，疲劳裂纹萌生并快速扩展，最后导致钻铤断裂。

Drill collar of a gas well in Sichuan-Chongqing fractured. The causes of fracture on drill collar were analyzed by means of macro analysis, scanning electron microscope analysis, metallographic examination, chemical composition analysis and mechanical property test, combined with field service conditions. The results show that the fracture type of drill collar was corrosion fatigue fracture. The main reason was that the sealing of the main shoulder surface of drill collar was poor, which caused the drilling fluid to erode the shoulder surface and the root of the external thread to form corrosion pits. During the rotary drilling of the drill, the fatigue crack initiated and grew rapidly under the combined action of cycle stress and corrosion, and finally led to the fracture of drill collar.