针对S135钻杆在作业中发生两次断裂的典型案例，结合钻具服役的井下工况条件，对断裂钻具的断口形貌、材料的化学成分、力学性能等进行了测试分析。结果表明，该井H2S分压超过0.34 kPa，S135低合金钢钻杆的硬度远高于22 HRC，而断裂位置处于拉应力集中部位、其环境温度20~40 ℃又是硫化物应力开裂易发生的最敏感范围，受多种因素的综合影响，导致H2S应力腐蚀开裂的形成，造成了该井S135钻具的两次断裂。

Aiming at a typical case that S135 drill pipe fractured twice in working process, combining to the service conditions, the fracture morphology, chemical composition, mechanical properties and other properties of the drill pipe were tested. The results show that H2S partial pressure of the well exceeded 0.34 kPa, and the hardness of S135 low alloy steel drill pipe was more than 22 HCR. The fracture position was located in the tensile stress concentration position. The environmental temperature was 20-40 ℃ which is a sensitive range for sulfide stress cracking to occur. Affected by a variety of factors, H2S stress corrosion cracking formed, and resulted the fracture of S135 drill pipe.