An insight into modeling wellbore stability using the extended Mogi-Coulomb criterion and poly-axial test data

The cost of drilling oil and gas wells is likely to be charged by billions of dollars each year due to wellbore stability problems. In engineering practice, a linear poroelasticity stress model in combination with a rock strength criterion is commonly used to determine a minimum mud weight for stable well drilling. In this paper, new models for predicting the stability of vertical wellbores using the nonlinear form of Mogi criterion and poly-axial test results were perfumed. Afterward, by applying analytical models to the real field data, the applicability of the models has been verified. From comparing the results of this nonlinear and the liner Mogi-Coulomb criterions, the impact of the nonlinearity on the wellbore stability prediction has been identified. Thus, the results of nonlinear form of Mogi failure criterion were very close to the field mud weight used to successfully drill the borehole.