Comparative Study of Failure Criteria to Determine Safe Mud Weight Window in one of the oil wells southwestern Iran

Proper determination of the safe mud weight window is important in order to reduce the risk of mud loss and also reduce the risk of well eruption and ultimately will create safe drilling and increase the speed of drilling operations. In this research, one of the wells of the Maroon oil field in southwestern Iran has been investigated as a case study. To estimate the geomechanical parameters, including the mechanical parameters of the rock, the pore pressure, as well as the stresses of the region, sound well loges and proper experimental relationships have been used for the field. After estimating the geomechanical parameters and constructing the geomechanical model, the constructed model is validated to ensure accuracy. After preparing a valid geomechanical model, the stability of the well is analyzed using the two criteria of Mohr-Columbus and Mogi-Columbus failure, and the application of the above criteria in determine " mud weight safe window" is compared. The results show that the Moggi-Columbus criterion better than the Mohr-Columbus criterion recognizes the fractures created in the studied well, such as the Breakout event. To validate the geomechanical model and confirm the efficiency of the empirical criteria used in detecting the breakout event, numerical simulation of wells in two steps of geostatic and drilling was performed. The simulation results indicate the formation of a breakout event in the depth of the study and thus confirm the method used in this paper.