Gas flow in shale reservoirs

Abstract

This study incorporates various gas transport mechanisms in shale nanopores with nonlinear and non-equilibrium gas adsorption- desorption kinetics. We formulate a simplified model for matrix and hydraulic fractures to study the dynamic production performance of multi-stage fractured horizontal wells in shale gas reservoirs. The gas transport mechanisms include viscous flow, Knudsen diffusion of free gas, surface diffusion, and slippage of adsorbed gas whilerock deformation is coupled in the flow equations. The sensitivity of the production rate to key physical parameters is examined through numerical simulation. Our results indicate that the viscous flow and Knudsen diffusion dominate the production of shale gas. The production rate was sensitive to the desorption rate while largely unaffected by the surface diffusion and slippage of the adsorbed gas, given that the transport process of adsorbed gas is a much slower process than the diffusion of free gas.