西部某气井油管螺纹脱扣失效分析

西部某气井使用的L80钢Φ88.90 mm×6.45 mm 外加厚油管螺纹接头发生了脱扣事故，为了探寻螺纹脱扣失效的原因，对失效样品进行了化学成分、拉伸性能、夏比冲击、洛氏硬度等理化性能检验，并对随机抽取的同批次未使用油管进行了螺纹检测、全尺寸试验等相关试验。结果表明，所用油管理化性能、螺纹参数、实物试验均符合相关标准要求，该失效为低载荷滑脱失效，主要是由于现场操作上扣过程中发生了错扣，引起油管螺纹粘扣，导致螺纹的连接强度大幅度降低。

Failure Analysis on Thread Tripping of Tubing in a Gas Well in Western China

The thread tripping failure occurred in the threaded joint of Φ88.90 mm×6.45 mm L80 externally thickened tubing used in a gas well in western China occurred. In order to find out the causes of thread-tripping failure, chemical composition, tensile properties, Charpy impact, Rockwell hardness and other physical and chemical properties of the failure samples were tested, and the same batch of unused tubing randomly selected were tested for thread detection, full-scale test and other related tests. The results show that the management performance, screw thread parameters and physical test of the tubing meet the requirements of relevant standards. The failure is a low-load thread stripping case and the main cause for such failure is thread gluing which result in the reduction of the connection strength. The reason caused the thread gluing is thread alternating which occurred during the making-up process.