Modeling of Compositional Gas Transport in Shale as a Deformable Porous Medium

Commercial production from resource shale has been realized largely due to the creation of propped hydraulic fractures in these unconventional resources. However, the pore pressure declines during production, resulting in a decrease in the fracture width and conductivity. This is because of the matrix and proppant deformation, and consequent embedment of proppants in the shale matrix. We present a new mathematical model and simulation framework to model multicomponent advection and molecular diffusion in a deformable shale medium using the control volume finite element method.We use the Maxwell-Stefan diffusion theory to model the composition- and pressure-dependence of molecular diffusion, while we use a continuum with viscoelastic properties to model the stress and time-dependence of the propped fracture conductivity. The study shows that shale-gas well production creates a non-uniform stress field near the fracture surface. This production-induced stress field tends to close the hydraulic fracture and decrease its aperture over time.