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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。
In order to optimize the rock strength criterion for wellbore collapse pressure prediction, based on the comprehensive evaluation of the MC, MG-C and E.MG-C criterion characteristics, combined with the geostretgic stress in the borehole elastic formation, Pressure with the azimuth, the inclination angle of the law of change. The results show that the predictions of the MC criterion ignoring the intermediate principal stress are too conservative and the linear MG-C criterion yields the lowest value of collapse pressure. The E.MG-C criterion considering the non-linear failure characteristics of the rock high stress region has a good prediction result. However, The predicted results of E.MG-C criterion will be less than those predicted by MG-C in the case of high inclination, which reflects the influence of nonlinear failure characteristics of rock on collapse pressure of shaft lining. Under different stress conditions, the best trajectory of the wellbore is located in the maximum and minimum stress plane, and parallel or biased to the direction of maximum stress. The stress distribution in situ and the actual wellbore state are also largely determined Wellbore stability. The research results are helpful to provide more accurate and comprehensive advice for drilling engineering design and well trajectory optimization.