水平井膨胀管螺纹失效风险分析

Analyses on Failure Risk of Expansion Pipe Threads in Horizontal Wells

由于膨胀管需要下入水平井中,水平井井眼曲率和水垂比均较大,膨胀管螺纹连接处壁薄强度弱,在施工过程中极易发生断脱,为此对膨胀管下入水平井的风险和可行性进行分析。以某井眼为例,利用有限元软件对螺纹进行下入强度计算、螺纹连接的屈服极限计算以及螺纹连接的拉伸极限计算,并搭配室内模拟实验,判断螺纹连接是否出现失效风险,进而判断膨胀管下入水平井的可行性。研究结果表明:通过对比30 m膨胀管无螺纹连接的应力应变情况,30 m有螺纹连接的膨胀管的最大应力未超过材料的许用应力;螺纹连接的屈服极限计算和拉伸极限计算结果显示,螺纹连接均达到极限状态。室内模拟实验结果显示膨胀管实验过后符合膨胀管补贴要求,研究结果对膨胀管长水平段补贴以及制定配套的施工工艺规范具有重要指导意义。

Because expansion pipe needs being placed down the horizontal wells,borehole curvature and water vertical ratio are both large,and thread connection walls of expansion pipes are thin and weak in strength,it is easy to break off in the process of construction,so this paper conducts analyses on the feasibility and risk of expansion pipe to be set in the horizontal wells.With one wellbore as an example,finite element software is applied to the intensity calculation of thread lowering in the well,the quotation limit calculation of thread connection and the stretching limit calculation of thread connection.Meanwhile,combined with laboratory simulation experiment,by judging whether thread connection exists the risk of failure,the feasibility of expansion pipe lowering in the horizontal well is further determined.The results show that compared with stress changes of 30 m expansion pipe without thread connection,30 m expansion pipe with thread connection has the largest stress,which doesn’t exceed the allowable stress.The results of quotation limit calculation and the stretching limit calculation about thread connection show that both thread connections reach the limit status.Laboratory simulation experiment results show that expansion pipes after experiment conform to subsidy requirements,and research results have important guiding significance in the horizontal segment subsidy of expansion pipe length and the establishment of matching construction technology standards.