空气钻井过程中钻杆断裂原因分析

Cause analysis of drill pipe fracture in air drilling

川东北1区在空气钻进过程中发生了多起钻具断裂事故。为了搞清钻杆断裂原因,对空气钻井过程中钻具断裂事故进行了调查研究,并对一根断裂钻杆进行了失效分析。失效分析内容主要包括断口宏观分析和微观分析,钻杆材料化学成分、力学性能和金相组织试验分析,钻杆在空气钻井过程中受力条件分析等。失效分析表明,钻杆属于早期疲劳断裂,断裂主要原因是在空气钻井过程中钻具受到的震动载荷远大于钻井液钻井过程中的震动载荷,在交变的震动载荷作用下,钻具容易产生疲劳裂纹;由于现有的井口检测仪表不能精确及时反映钻杆刺穿之后产生的泵压变化,无法及时采取预防措施,疲劳裂纹不断扩展,最终导致了钻杆断裂失效。

Several drilling tool fracture accidents took place during air drilling in one oil field. In order to know the cause of the accidents, an investigation is taken and the failure analysis is carried oat for one broken drill pipe. The fracture analysis includes the macro-fractography and micro-fractography, the experimental analysis of the chemical components, the mechanical properties, and the metallography of drill pipes, and the stress conditions analysis of drill pipes in air drilling. It is considered that fatigue crack is early produced on drill pipes, because the vibration load of drilling tools in air drilling is more severe than that in mud drilling. Fatigue cracks easily occur under alternating vibration. Because the current wellhead detecting instruments can not be used to reflect the change of pump pressure produced after drill pipe piercement timely and accurately, effective measures can not be taken in time to prevent the expansion of fatigue cracks. As a result, drill pipe fracture accidents occur.