The Role of Geomechanics Behaviors on Wellbore Collapse and Sanding Prediction in Gas Reservoir

Abstract Critical plastic strain and stress at a wellbore wall are identified and commonly utilized in sanding and wellbore collapsing pressure prediction. Extensive experimental testing results suggest that the critical pressures of wellbore collapsing and sanding onset calculated based on statically determined stresses, however, generate large margin when compared to the testing results. These existing models may suffer various shortcoming and an accurate prediction on sanding or wellbore collapsing pressure may require a model which reflects the fundamental behavior. An elasto-plastic model with non-associated plastic flow and stress or strain-dependent failure/sanding criteria are re-visited, simplified analytical solutions of stresses, strain and critical pressure, solution procedure for sanding by incorporating all these fundamental mechanical behavior are developed. A critical effective plastic strain model is utilized and CEPS subject to different external/internal loading are calculated and validated against hollow cylinder testing results. Analytical solutions with nonlinear and linear yielding criteria are applied. These simulating results are compared to those results of THC tests and a geomechanical model with consideration of stress-deformation rather than with stress only is recommended for wellbore collapse and sand predictions.