某S135钻杆管体断裂失效原因分析

针对某井下S135钻杆管体出现的断裂失效现象，通过无损检测、化学成分、力学性能、金相以及旋转弯曲疲劳寿命试验分析等方法，对S135钻杆出现断裂失效的原因进行了分析。分析认为，钻杆在腐蚀介质下产生腐蚀坑，在交变载荷的作用下，腐蚀坑底萌生疲劳裂纹并扩展，最终导致钻杆管体断裂失效。建议对该批钻杆进行外表面磁粉及超声波无损探伤检测，以避免带有裂纹的钻杆下井使用；当钻速发生数量级的突变时，应对钻遇岩层的岩性和钻头的磨损程度进行综合分析，及时起钻检测钻头，避免同一钻杆在复杂位置长时间工作。

Fracture Failure Analysis of a S135 Drill Pipe Body

Aiming at the fracture failure phenomenon of a S135 drill pipe body, the failure causes of S135 drill pipe fracture were analyzed by non-destructive testing, chemical composition, mechanical properties, metallographic and rotational bending fatigue life test analysis. The analysis results show that the drill pipe produces corrosion pits under corrosive medium. At the same time, under the action of alternating load, the fatigue cracks are generated at the bottom of the corrosion pit and expand, which eventually leads to failure of the drill pipe body. It is recommended that the drill pipe be subjected to magnetic powder and ultrasonic non-destructive testing on external surface to avoid the use of cracked drill pipe downhole. When the drilling speed is changed by a magnitude, the lithology of the rock encountered by the drill bit and the wear degree of the drill bit should be comprehensively analyzed, and the drill bit should be taken out to detect the drill bit in time to avoid the same drill pipe working in a complicated position for a long time.