Structural heterogeneities and tectonic forces in NE India give rise to changeable in situ stresses with varying orientations in this part of India. Wells located in the seismic gap in Upper Assam, the Naga Thrust and the Chittagong–Mizoram–Tripura fold belt of Mizoram are used to study stress state and borehole collapse models for the area. The absence of stress studies in the Mizoram area acts as an impetus to undertake stress studies. Poroelastic modelling shows the average ratio of maximum horizontal to vertical stress to be 0.79 for normal-faulted, 1.18 for thrust-faulted and 1.12 for strike-slip-faulted regimes. The S_H direction varies from 193°N in Upper Assam to 213°N in Mizoram areas. The image log from a well in the Mizoram area shows the rotation of S_H direction (c. 85°) to vary from 500 to 3707 m due to structural heterogeneity. The thrust and strike-slip regimes in the study area pose the major threat for safe borehole drilling in this complex terrain. To mitigate this issue, Mohr–Coulomb (MC) and Mogi–Coulomb (MG) rock failure criteria are discussed to predict the minimum mud weight required for borehole drilling. MG-predicted mud weight (MW) ensures borehole stability in wells in normal-faulted sediments, while MC-predicted MW prevents shear failure in wells in thrust and strike-slip regimes. A disc plot is used to model a stable wellbore drilling path with a minimum MW. A vertical well is shown to be stable in a normal-faulted regime, whereas horizontal drilling is preferable in the fold–thrust belt. Sensitivity analysis of geomechanical input parameters on MW using Monte Carlo simulation shows that S_H has the maximum effect on MW regardless of the faulting regimes.

印度东北部的结构异质性和构造力导致印度该地区具有不同方向的地应力变化。位于上阿萨姆邦地震间隙、Naga 逆冲断层和米佐拉姆邦吉大港-米佐拉姆-特里普拉褶皱带的井用于研究该地区的应力状态和井眼坍塌模型。米佐拉姆地区缺乏压力研究是进行压力研究的动力。多孔弹性模型显示，正常断层的最大水平应力与垂直应力的平均比率为 0.79，推力断层为 1.18，走滑断层为 1.12。S _H方向从上阿萨姆邦的 193°N 到米佐拉姆地区的 213°N 变化。米佐拉姆地区一口井的图像测井显示了S _H方向 ( c. 85°）由于结构异质性，从 500 到 3707 m 变化。研究区的逆冲和走滑状态对这一复杂地形的安全钻孔构成了主要威胁。为了缓解这个问题，讨论了 Mohr-Coulomb (MC) 和 Mogi-Coulomb (MG) 岩石破坏标准，以预测钻孔所需的最小泥浆重量。MG 预测的泥浆重量 (MW) 可确保正常断层沉积物井中的井眼稳定性，而 MC 预测的 MW 可防止井在逆冲和走滑状态下发生剪切破坏。圆盘图用于模拟具有最小 MW 的稳定井眼钻井路径。垂直井在正常断层状态下被证明是稳定的，而在褶皱-逆冲带中水平钻井是优选的。使用蒙特卡罗模拟对 MW 地质力学输入参数的敏感性分析表明，无论断层状态如何， S _H对 MW 的影响最大。