Accommodating non-darcian effects of slip flow and knudsen diffusion on gas flow for use in reservoir simulations

Abstract

Systems and methods include a method for using reservoir simulations. Permeabilities are measured from a rock sample at different pressures using single-component gas and bulk gas viscosity values. The rock sample is representative of rock used in a reservoir simulation. For each gas component of reservoir gas, porosities are determined, including determining mean free paths for a range of temperatures and pressures encompassing conditions for both reservoir simulation input and the measured permeabilities. A characteristic pore radius for the rock is determined using the measured permeabilities and the determined porosities. Viscosity adjustment factors for a predefined range of temperatures and pressures are determined using the measured permeabilities. Adjusted gas viscosities for the predefined range of temperatures and pressures and the measured permeabilities are determined using the viscosity adjustment factors. The reservoir simulator is executed using the adjusted gas viscosities.