Given that drilling operations are among the major challenges in the oil and gas industry and hold significant importance, drilling must be carried out in a manner that prevents the waste of incurred costs and avoids issues such as wellbore collapse, pipe sticking, and similar problems. In other words, the wellbore must remain stable. Wellbore instability is one of the key issues encountered by drilling engineers, and each year, several wells fail to reach production due to this problem. One of the modern approaches recently adopted in Iran is geomechanics, which in this study is applied as an advanced numerical modeling method to overcome wellbore instability and ensure safe drilling operations. Wellbore stability analysis is conducted by collecting data such as in-situ stresses, reservoir and well pressures, and the mechanical properties of the formation and drilling fluid. These data are then used to construct a numerical geomechanical model that significantly contributes to evaluating potential risks in the drilling of future wells. In this study, it was determined that drilling operations were performed under overbalanced conditions, leading to drilling fluid invasion into the formation. Based on the calculated safe drilling mud window, it was concluded that no wellbore collapse would occur. Keywords: Geomechanics, In-situ stress, Drilling mud window, Wellbore instability