某井偏梯形螺纹接头脱扣原因分析

某直井发生接箍工厂端偏梯形特殊螺纹套管滑脱,下部套管柱落井未能打捞出。针对此起脱扣事故,采用理论与试验相结合的方法,对脱扣接箍的化学成分和力学性能进行了分析和测试,对同批次两组套管试样螺纹参数进行了测量和实物试验,另外对脱扣接箍工厂端和现场端以及同批次新接箍工厂端内螺纹承载面和导向面处显微组织进行了比较。结果表明,接箍工厂端上扣扭矩过小是导致套管脱扣失效的主要原因,同时文章也说明螺纹接触处的显微组织比较分析法是解决此类问题的一个重要手段。

Pullout cause analysis of buttress thread connection for a well

A buttress premium thread casing joint was pulled out from mill end of a coupling in a straight well,and dropout casing string couldn’t be got out of the well.The research on this pullout case was carried out by combining relative theory with test.The chemical composition and mechanical properties of the pullout coupling were analyzed and tested.Thread inspection and full-scale test were done for two casing simples of the same lot.Metallograph comparison analysis was carried out on load flank and guide flank of box thread at mill end and field end of pullout coupling and mill end of the new coupling same lot.The results show that the dropout failure is due to too little make up torque at mill end of coupling,at the same time microstructure on contact surface of thread comparison analysis method is a important means to solve this case.