套管钻井扭转残余应力对套管抗挤强度的影响

Impact of Casing Drilling Residual Torsion Stress on Its Casing Collapse Strength in Casing Drilling

套管钻井中套管管柱的旋转动力来自井口所施加的扭矩。讨论了在套管钻井中不同扭矩下扭转状态的确定方法,对应不同的扭矩,套管具有弹性、弹塑性和塑性三种不同的扭转状态;讨论了不同扭转状态下残余应力的分布情况,计算了在弹塑性扭转和塑性扭转情况下的平均残余应力,推导了考虑残余应力影响下的套管抗挤强度修正公式。算例分析结果显示,在发生弹塑性扭转的情况下残余应力使套管抗挤强度下降了0.033%,在保证管体不发生几何形状改变的条件下,可忽略残余应力对套管抗挤强度的影响。

Casing strings are rotated by torque from wellhead during casing drilling. The method to determine torsion status under various torqueses in casing drilling was discussed. There are three different torsion statuses under different torques, including elastic torsion, elastic-plastic torsion and plastic torsion. The residual stress distribution was also discussed under different torques. The average residual stress under elastic-plastic and plastic torsion status was calculated. The modified casing collapse strength formula was derived considering the effect of residual stress. The analysis of calculation results indicates that the residual stress caused the collapse strength to decrease 0. 033% under elastic-plastic torsion, and effects of residual stress on casing collapse strength can be neglected when there is no geometry shape change in the casing