| G105钢级钻杆外螺纹接头裂纹原因分析 |
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| 引用本文： | 龚丹梅,余世杰,袁鹏斌,高连新.G105钢级钻杆外螺纹接头裂纹原因分析[J].石油矿场机械,2014(10):39-44. |
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| 作者姓名： | 龚丹梅 余世杰 袁鹏斌 高连新 |
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| 作者单位： | 上海海隆石油管材研究所;西南石油大学材料科学与工程学院;华东理工大学; |
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| 摘 要： | 某油田在定向钻井作业过程中有多根G105钢级钻杆外螺纹接头出现断裂和裂纹。对该井钻杆使用情况进行调查研究,并对1根螺纹牙底有裂纹的外螺纹接头进行失效分析。失效分析内容主要包括断口观察、钻杆接头材料化学成分分析、力学性能及金相组织分析,并通过有限元方法模拟分析API标准NC31接头受到复合载荷时的应力分布状态,比较NC31接头标准外径与增大外径时外螺纹接头螺纹牙受力情况。分析结果表明:接头螺纹牙底裂纹为疲劳裂纹,钻杆接头外螺纹大端第1~3牙为应力集中区域。由于在该定向井造斜点附近井眼全角变化率较大,存在较大的结构弯曲,使接头承受较大的交变复合载荷,最终在接头螺纹应力集中区萌生疲劳裂纹,导致失效。
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| 关 键 词： | 钻杆 螺纹 疲劳裂纹 失效分析 |
Cause Analysis on Pin Joint Ctack of G105 Gtade Dtill Pipe |
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| Affiliation: | GONG Dan-mei, YU Shi-jie, YUAN Peng-bin, GAO Lian-xin (1. Shanghai Hilong Oil Tubular Goods Research Institute, Shanghai 200949, China ; 2. College of Materials Science and Engineering, Southwest Petroleum University, Chengdu 610500, China ; 3. East China University of Science and Technology, Shanghai 200237, China) |
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| Abstract: | Several G105 grade drill pipe tool joints fractured and cracked in process of directional drilling in a certain oil field.The drill pipe service condition and conducted failure analysis on one cracked pin joint were investigated.The failure analysis was performed based on macro and micro morphology analysis,material chemical composition test,mechanical property test,metallographic microstructure analysis,stress state analysis of API NC31 under combined loads and compared to the increased OD model.Analysis results show that the crack is fatigue crack.The first to the third engaged threads section on the big end of pin tool joint is region of stress concentration.The overall angle change rate near the kick off point was pretty large,which led to fatigue cracks at the region of stress concentration under the combined effects of axial tensile stress and repeated bending stress. |
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| Keywords: | drill pipe thread fatigue crack failure analysis |
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