The current study proposed an improved approach for application of Geomechanical Units (GMUs) classification in reducing the uncertainty of wellbore stability models. For this purpose, the optimal drilling direction and safe mud window were modeled in the Iranian Offshore oilfield, Persian Gulf basin. Two main normal faults created a graben with three geomechanical sectors in the study area including northern, middle and southern sectors. The middle sector, which is under high compression, is the main target of this study. A set of well logs and Fullbore Formation Micro Imager (FMI) data associated with the rock mechanical tests including Uniaxial Compressive Strength (UCS), Triaxial Compressive Strength (TCS) and ultrasonic results were used to establish and tune the geomechanical models. The dynamic rock elastic moduli including UCS, Poisson's ratio, Young's modulus, shear modulus and bulk modulus were estimated from well logs data. Through appropriate correlations between well logs and laboratory results, the dynamic modules were converted to static data. Five geomechanical units were obtained based on the classification of rock elastic moduli by using multi-resolution graph-based clustering.

The interpretation of FMI logs and their incorporation in the geomechanical models showed that most safe drilling direction is in the 120° azimuth which is parallel to the direction of minimum horizontal stress, σ_h (NW-SE direction). Higher mud weight is expected at N030E azimuth to overcome collapse pressure, which is the worst drilling direction, σ_H (NE-SW direction). Wellbore inclination more than 60° angle is not recommended for formations comprising of GMU E and partially GMU D (mainly shales and clayey limestones). The results of this study showed that GMUs classification is an effective way of updating the wellbore stability models and reducing the uncertainty of safe mud window design.

当前的研究提出了一种改进的方法，可应用于地质力学单元（GMU）分类，以减少井眼稳定性模型的不确定性。为此，对伊朗海上油田波斯湾盆地的最佳钻井方向和安全泥浆窗口进行了建模。两条主要的正断层在研究区域内形成了三个地质力学区域，包括北部，中部和南部部分。本研究的主要目标是处于高压缩状态的中间部门。与岩石力学测试相关的一组测井和全孔地层显微成像仪（FMI）数据，包括单轴抗压强度（UCS），三轴抗压强度（TCS））和超声结果用于建立和调整地质力学模型。根据测井资料估算了岩石的动态弹性模量，包括UCS，泊松比，杨氏模量，剪切模量和体积模量。通过测井和实验室结果之间的适当关联，将动态模块转换为静态数据。通过基于多分辨率图的聚类，基于岩石弹性模量的分类，获得了五个岩土力学单元。

FMI日志及其在地质力学模型掺入的解释表明，大多数安全钻井方向是在120°方位平行于最小水平应力，σ的方向_ħ（NW-SE方向）。更高泥浆重量预计在N030E方位角克服坍塌压力，这是最差的钻孔方向，σ _ħ（NE-SW方向）。对于由GMU E和部分GMU D（主要为页岩和粘土质石灰石）组成的地层，建议不要将井眼倾角控制在60°以上。这项研究的结果表明，GMUs分类是更新井眼稳定性模型并减少安全泥窗设计不确定性的有效方法。