A Method to Find Optimum Mud Weight in Zones With No Safe Mud Weight Windows

Rising demand in higher productivity as well as reducing drilling damages has encouraged companies to use mechanical earth modeling (MEM) for developing fields. Conventionally, in a safe mud weight window there are four different bounds which are employed by drillers to avoid possible operational challenges such as kick, loss, breakout and breakdown. However, there are sometimes zones where the boundaries are transgressed to one another and a safe mud weight window cannot be determined. In this study, we presented a numerical solution to calculate the optimum mud weight by defining an indicator for growth of the plastic zone around the borehole by using an elastoplastic model which provides more realistic evaluations of wellbore integrity than linear elastic model. Results showed the proposed method finds the mud weight which is high enough to tolerate the breakouts and yet low to attenuate mud losses. Method was utilized in a real case and results were then compared with the drilling data and verified the efficiency of the presented methodology.