Coupling a void growth model with an elastoplastic material model for a simultaneous prediction of the borehole plastic zone and critical collapse pressure

Abstract

The elastoplastic shear stability of an inclined borehole is explored in this study. Unlike other previously published elastoplastic wellbore stability solutions, this work considered the contributions of the anti-plane shear stresses. A new framework for estimating the critical elastoplastic collapse pressure and the extent of the plastic zone around the borehole is presented. In this approach an elastoplastic material model is coupled with a void-growth model to simultaneously predict the collapse pressure and plastic zone. In this paper, the Gurson void-growth model is coupled with an elastic-brittle plastic material model, and the critical collapse mudweight and plastic radius at the orientation of maximum compression are solved simultaneously from the resulting system of equations. The predicted collapse mudweights from the proposed approach compared very well with observed field data. When compared with the conventional method (NYZA = 1), the proposed framework performed better, although the difference can be negligible in some cases.