What Difference Does Selection of Failure Criteria Make in Wellbore Stability Analysis?

Selection of the appropriate rock failure criteria is one of the key steps in determining minimum drilling fluid density in wellbore stability analysis. Numerous failure criteria have been used for rock failure analysis but there is no common agreement of which failure criterion to use. In this paper, the thirteen most common rock failure criteria were compared. The rock failure criteria were evaluated for three lithologies. A statistical analysis was performed to determine the similarities and differences among the failure criteria. According to the results, Tresca, Von Mises, and Inscribed Drucker-Prager estimated the higher bounds for the minimum required mud weight for all cases. Although Circumscribed Drucker-Prager usually predicts the lower bounds for the minimum required mud weight, its results are in the middle range for hard formations with low internal angle of friction. Modified Lade, Modified Wiebols-Cook and Mogi-Coulomb provided similar results for the three cases studied, so these failure criteria may be used interchangeably without changing the results