渭河水平定向钻穿越钻杆疲劳断裂分析

渭河水平定向钻穿越工程是西气东输二线的重点工程,在穿越过程中进行第六级扩孔时出现钻杆断裂情况,导致穿越失败。从失效钻杆的断口形式、化学成分和力学性能方面分析属于疲劳断裂破坏。文章从疲劳破坏的机理出发,按照疲劳理论的新进展即应力幅验算方法,采用通用有限元分析软件计算钻杆工作时的最大和最小应力等,得出钻杆与扩孔器连接处受交变应力的影响易产生疲劳破坏的结论,并根据疲劳计算方法得出允许应力循环次数,该数值与工程实际相符。利用有限元软件和应力幅值可预测定向钻钻杆的使用寿命,对油气管道水平定向钻施工具有一定的实际意义。

Fatigue Failure Analysis of Drilling Pipe for Weihe River Horizontal Directional Drilling Project

The Weihe River HDD project is a key project of the Second West-East Gas Pipeline. During the HDD project construction, the drilling pipe cracked in the sixth reaming operation and the operation failed.It was judged as a fatigue failure by investigating the broken cross-section style and the chemical composition and mechanical properties of the failed pipe. Based on the fatigue failue mechnism and according to a newly developed fatigue theory ?the stress amplitude method, this paper calculates the minimum and maximum stresses of the drilling pipe by a general-purpose FEM software and concludes that the alternative stress at the connection of drilling pipe and reamer was able to cause the fatigue failure easily, the allowable stress cycle index from the fatigue calculation method agreed with that from the engineering practice. It shows that the service life can be predicted by means of FEM software and stress amplitude, which is useful to practical HDD construction.