中文摘要：

气体钻井中钻具失效事故频发,严重阻碍了气体钻井技术的规模化应用。通过现场调研发现,气体钻井钻具失效率为钻井液钻井钻具失效率的2-10倍,且在钻杆、加重钻杆、钻铤处均有发生,脆断特征明显。定性分析了导致气体钻井钻具失效的主要因素,包括工作载荷、振动、热效应、冲蚀、腐蚀、井径扩大和冲击。指出剧烈振动和热积聚是除工作负载以外引起钻具异常失效的主要因素,其次是冲蚀、腐蚀和井径扩大。动载效应和钻具局部热效应的耦合作用达到一定程度后,钻具局部产生裂纹,然后在上述因素的综合作用下,裂纹快速扩展,钻具发生脆断。

英文摘要：

Drill-string failures occur frequently during gas drilling, which seriously restricted the large scale application of gas drilling technology. In-situ investigations indicate that frequency of drill-string failure in gas drilling wells is 2--10 times as many as that in mud drilling wells. In addition, the failures occurred in drill pipe, drill collar, and heavy weight drill pipe with characteristics of brittle fracture. This paper analyzed qualitatively the main factors causing drill-string failure accidents in gas drilling wells, including working load, vibration, thermal effect, erosion, rusty, hole enlargement and impact. The paper pointed out that the reasons for-failure are working load, vibration and thermal accumulation, followed by the erosion, rusty, hole enlargement and impact. When dynamic effect and local thermal effect combined to a certain degree, drill-string crack arises, and then the crack expands rapidly due to above impacts, re suiting in drill-string brittle fracture.