The oil industry and drilling operations are extremely important in today's life. One of the fundamental challenges in drilling oil wells is the issue of wellbore stability, which can sometimes lead to significant costs, including financial expenses as well as safety risks for personnel. The main concern of a drilling engineer is to maintain the well in safe conditions and prevent the collapse of the wellbore walls, which necessitates special attention to the drilling fluid program, casing design, and operational methods in drilling a well. This study examines the stability of oil well walls and the factors affecting it. To this end, using the logs derived from the formation under study, the formation data was first calculated, and then, using a geomechanical model of the formation in the ABAQUS finite element software, the wellbore stability was analyzed and the optimal drilling fluid weight was determined under various conditions. To this end, using ABAQUS software, a geomechanical model of a vertical well at a depth of 2600 to 2700 meters from the ground surface was simulated, and the optimal drilling mud pressure, at which no plastic zones form in the wellbore, was calculated. The lower limit of the optimal drilling mud pressure, determined through simulation in ABAQUS software, was calculated as 33.1 MPa, and the upper limit of the mud pressure was calculated as 121.7 MPa. The results indicate the efficiency of ABAQUS software in analyzing the stability of oil wells.