Borehole instability consider to be one of the key concerns in petroleum industry due to various economic factors and thus stability analysis is necessary prior to any drilling operation. In order to have a successful drilling operation and avoid any waste on rig time and expense losses, several pieces of information such as fracture gradient, in situ stresses, formation pressure, and well trajectory must be thoroughly understood The majority of wellbore stability issues in the globe are caused by shale rock. In Oman, for example, Nahr Umr shale formations are responsible for a substantial amount of Petroleum Development Oman's (PDO) drilling issues. In order to perform any wellbore stability analysis, several elements that affect shale stability must be addressed and thoroughly investigated. The relationship between the applied mud, formation pore pressure, rock mechanical properties, and in situ stress state, which is inadequately covered in general practice, is required for such an analysis. In PDO, currently a trial-and error approach for increasing mud weight is taken on when instability issues noticed. Thus, a proper understanding of drilling experiences in conjunction with geomechanical considerations for the earth system is required in such approach. Therefore, up to date, there is no statical distribution in Nahr Umr formation for geomechanical analysis. The study is statistically describing and geomechanically analyzing the drilling operations in Nahr Umr shale formation to investigate the potential of instability in north and south Oman fields. In this regard, a three-dimensional Mogi-Coulomb wellbore stability model was utilized to evaluate the stability of wells in Nahr Umr shale formation all over Oman. Furthermore, a development of simplification for wellbore stability analysis in Nahr Umr shale formation was examined and the evaluation of optimum well trajectory for drilling in Nahr Umr shale formation was exposed.