圆螺纹套管接头发生脱扣主要与产品设计加工、材质性能、上扣扭矩或上扣位置以及现场操作等方面的因素有关.近几年,国产套管质量有了很大的提高,然而圆螺纹套管接头滑脱事故仍时有发生,导致了较大的经济损失和安全事故的发生.针对一起圆螺纹套管脱扣事故,采用理论分析与试验相结合的方法,对脱扣套管和接箍进行了宏观分析和材质理化性能试验,并对同批次套管试样进行了螺纹参数测量和实物拉伸模拟试验,最后对试验结果进行了综合分析.结果表明:现场上扣时夹持接箍位置错误、现场端上扣不到位是导致该套管脱扣失效的主要原因.

Pullout might happen to round thread casing connections for reasons of design and process of products,properties of material,make-up torque or make-up position and field operation problems.In recent years,Chinese casing properties had got a high improvement.But the numbers of casing connections pullout accident were not declined obviously.These led to great economy loss and safety hazard.Research on a round thread casing connection pullout case was carried out by combining relative theoretical analysis with test.Macroscopic analysis and material’s physical and chemical properties test were done to the casings and couplings.Thread inspection and full-scale tensile simulation test were done to casing samples that was the same lot with the pullout casing.Comprehensive analysis was carried out on these results at last.The results show that pullout failure was ascribed to two main causes.One was make-up location could not reach standard location at field end,and the other was incorrect holding position on coupling in the course of make-up.