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层理性地层中进行大斜度井施工的井壁失稳问题较为突出,在传统井壁稳定模型基础上,以弱面对岩石强度的弱化作用实验为依据,引入欧拉变换充分考虑三维地应力方向的任意性,利用Mogi-Coulomb准则强化中主应力对围岩本体强度的影响,结合单弱面强度准则建立分析层理性地层斜井井壁稳定问题的模型,并进一步给出计算斜井坍塌压力与破裂压力的方法与公式。实验与计算结果表明:当加载方向与弱面夹角为30°时岩石强度最低;Mogi-Coulomb准则因考虑了中主应力的影响而对围岩本体强度的估计更为有效;考虑层理弱面影响的井壁坍塌破坏区域明显增大,破坏位置也发生改变;取得最小坍塌压力值的钻井方向在空间中与层理面并非简单的垂直关系;空间中关于地应力主平面对称的井孔破裂压力相同。利用所建模型进行安全泥浆压力窗口的计算可为安全钻井以及斜井轨迹设计提供理论依据。
On the basis of the traditional wellbore stability model, based on the weakening effect of weakness on the rock strength, the Euler transformation is adopted to fully consider the three-dimensional in-situ stress Direction of arbitrariness, the use of Mogi-Coulomb criterion to strengthen the impact of the main stress on the strength of the surrounding rock body, combined with the weak surface strength criterion to establish stratified strata borehole wall stability model, and further gives the calculation of inclined shaft collapse Methods and formulas of pressure and rupture pressure. The experimental results show that the rock strength is the lowest when the angle between the loading direction and the weak plane is 30 °. The Mogi-Coulomb criterion is more effective in estimating the body mass of the surrounding rock due to the influence of the middle principal stress. The borehole collapse and damage area affected by the surface obviously increases and the damage location also changes. The drilling direction with the lowest collapse pressure value is not a simple vertical relationship with the bedding plane in space. The wellbore symmetrically with respect to the principal plane stress in space Bursting pressure the same. The calculation of the safe mud pressure window using the model can provide a theoretical basis for safe drilling and deviated trajectory design.