Modeling the swelling of shale matrix in unconventional reservoirs

This study presents a coupled fluid flow and geomechanics model for modeling shale swelling to quantitatively investigate the effect of swelling on transport properties of rock matrix and fractures. The main objective is to quantitatively determine the effect of shale swelling on the oil recovery from the rock matrix. A numerical solution is presented to solve the coupled equations simultaneously for the phase pressure, fluid saturation, stress, and strain. We show that the mechanical properties of the rock matrix vary significantly as the result of water imbibition. The reduction of the fracture and matrix permeability and porosity due to swelling is considerable. This results in the reduction of more than 50% of the oil recovered from shale matrix. Hence, shale swelling should be prevented in any water injection operations.