某井油管脱扣原因分析

Analysis of Causes for Pull-out of Tubing as Used in a Certain Oil Well

针对某井用Φ88.9mm×6.45mm P110钢级NU油管脱扣事故进行深入调查研究,对脱扣的油管进行了宏观和微观形貌分析,对油管材质进行了理化性能试验,对该批次未使用的油管接头试样进行了参数测量。通过试验分析和研究,认为油管接头材质及螺纹参数符合标准要求,油管脱扣属于低载荷滑脱失效,滑脱失效的主要原因是由于粘扣和上扣不到位导致接头的连接强度大幅度降低造成,而粘扣和上扣不到位的主要原因是上扣过程中发生了错扣。

For the thread-tripping failure of the Ф88.9 mmx6.45 mm P110 NU tubing as used in a certain oil well, an in-depth investigation is conducted, involving such activities as macro/micro morphology analysis of the failing tubing, physicochemical testing of the material, parameter measurement of the tubing connectors which are of the same product lot, but not yet used. Based on the testing and research results, it is identified that since both the material and the thread parameters of the tubing connector are up to applicable specification, the pull-out failure is defined as a low-load thread stripping case; and that the main causes for such a failure are thread galling and inappropriate thread making-up of the connector, which result in tremendous reduction of the connection strength; and what caused the thread galling and inappropriate thread making-up mistakes is just thread alternating as occurred during the making-up process.