略论套管螺纹密封性能与联接应力的关系

对套管螺纹的上紧过程以及在内、外压力作用下，接箍和管端上所产生的应力作了理论分析，给出了屈服上紧圈数、防漏上紧圈数、螺纹锥度公差的影响圈数和组合应力等的计算公式。简要地介绍了美国石油学会防泄漏工作组根据组合应力的大小，评价各种套管的有关问题。指出ＡＰＩ圆螺纹套管的固有缺陷使其防泄漏能力已不能适应高压油井，特别是高压气井的要求，因此建议在这些井中采用特殊螺纹套管。

Relation of the sealing ability of casing threads to connection stress

The tightening of casing threads and the stress on the casing coupling and pipe end under the action of internal and external pressure are analyzed, and the equations for calculating the yielding tightening turns, leakproof tightening turns,taper-tolerance-affected turns and composite stress are presented.And it is pointed out that, due to their inherent defect,casings with API round threads cannot meet the leakproof requirement of high-pressure oil wells and high-pressure gas wells,therefore casings with special threads should be used in these wells.