某水平井在泥浆循环过程中发生一起S135钻杆断裂事故, 为查明钻杆断裂原因, 对事故进行了调查研究, 并取样进行了包括断口分析、化学成分分析、力学性能测试、金相检验等一系列失效分析。结果表明: 该钻杆所处井段井眼全角变化率较大, 钻杆外壁受到严重磨损划伤并形成疲劳裂纹, 在较大扭矩和拉伸载荷作用下, 钻杆最终发生了断裂。

The rupture accident of one S135 drill pipe happened during mud circulating in horizontal well. In order to find out the fracture cause, an investigation was conducted and failure analysis was performed based on fracture analysis, chemical composition analysis, mechanical property testing, metallographic examination and so on. The results showed that the overall angle change rate of the accident well section was large, and the failure drill pipe was severe wear and scratched where fatigue cracks were formed, then under the torque and tensile loads, the drill pipe ruptured from fatigue cracks.