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建立了弱面地层数学模型，分析了斜井井壁岩石应力状态，推导出了井壁岩石最大主应力与低强度地层（弱面地层）法向夹角的计算公式，建立了用于大倾角地层钻井液密度安全下限的力学模型，详细分析了倾斜地层的倾角和走向对井壁稳定性的影响。研究结果表明，弱面地层的存在易使井壁失稳。对斜井来说，地层走向、地层倾角、井斜方位和井斜角不同，其井壁稳定性也不同。将打直井改为斜井，可以提高井壁的稳定性，也有利于安全钻进
The mathematic model of weak zone stratum is established. The rock stress state of inclined shaft wall is analyzed, the formula of the maximum principal stress of rock shaft and the normal angle of low-intensity stratum (weak zone stratum) is deduced, The mechanics model of lower bound of drilling fluid density safety in formation is analyzed in detail, and the influence of inclination and strike of inclined formation on the stability of wellbore is analyzed in detail. The results show that the presence of weak-surface formation is likely to destabilize the borehole wall. For inclined wells, the stratum direction, stratigraphic dip, well inclination angle and well inclination angle are different, and their borehole stability is also different. Changing a vertical well to an inclined well can improve the stability of the well wall and also facilitate safe drilling