中文摘要：

为了优选井壁坍塌压力预测的岩石强度准则,在综合评价M-C,MG-C和E.MG-C准则特点的基础上,结合孔弹性地层井周地应力,对保持井壁稳定的临界井底压力随方位角、井斜角的变化规律进行研究。结果表明：忽略中间主应力的M-C准则预测结果过于保守,线性MG-C准则得到了坍塌压力的最低值,考虑岩石高应力区非线性破坏特征的E.MG-C准则预测结果居中,但在高井斜角情况下,E.MG-C准则预测结果会小于MG-C的预测结果,反映出岩石非线性破坏特征对井壁坍塌压力的影响。不同地应力状态下,最佳井眼轨迹均位于最大和最小地应力平面内,且平行或偏向于最大地应力方向,原地应力分布状况和井眼的实际空间状态也在很大程度上决定了井眼的稳定性。该研究成果有利于为钻井工程设计、井眼轨迹优化提供更加精确和全面的建议。

英文摘要：

In order to optimize wellbore shear failure criteria, this article, comprehensively, evaluated the application characteristics of Mohr-Coulomb criterion, MG-C criterion and E.MG-C criterion. Combining with stress distribution around the borehole inelastic strata, we investigated the wellbore stability critical bottom hole pressure variation with azimuth and inclination. Results show that the predicted pressure of M-C criterion which omits the intermediate principal stress is partial conservative, while the prediction results of linear MG-C criterion get the lowest collapse pressure; the results of E.MG-C criterion, which considering nonlinear rock failure characteristics in the high-stress area, have a middle value, but its prediction collapse pressure of wells with high angle is lower than the result of MG-C criterion. This feature reflected the influence of nonlinear rock failure characteristics to wellbore stability. Under altered in situ stress states, the optimal well trajectory always located in the maximum and minimum principal stress plane and parallel or inclined to the direction of maximum stress. The in situ stress distribution and the actual space state of the borehole also largely determine the stability of the borehole. The research in this paper is useful to provide more accurate and comprehensive advices.