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A Unified Convection-Diffusion Layered Model For Non-Ideal Rarefied Gas Flow In Nanoscale Porous Media
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, ECMOR XVI - 16th European Conference on the Mathematics of Oil Recovery, Sep 2018, Volume 2018, p.1 - 20
Abstract
Existing rarefied gas flow models cannot accurately characterize gas flow behaviors in nano-porous media by coupling various empirical rarefaction and diffusion coefficients. Also, almost all models overlook the importance of non-ideal gas effect on the flux and apparent permeability. In this work, a unified model for nonideal rarefied gas flow in nano-porous media has been developed. More specifically, a straight capillary tube consisting of a viscous flow zone and a Knudsen diffusion zone is sectioned by an analytically derived boundary. Subsequently, the apparent permeability is obtained by coupling weighted flow mechanisms and extended to the porous media considering the roughness, rarefaction, and real gas effect. It has been found the apparent permeability hardly change when pressure is over 10.0 MPa and pore size is larger than 100 nm. Sensitivity analysis shows the apparent permeability is strongly dependent on pore size and weakly dependent on roughness. Finally, it is observed that real gas effect decreases the flux of the new model at high pressures. The developed model is an easy-to-use tool for gas transport in tight porous media and can be integrated in large-scale simulations to optimize the long-term production performance of unconventional reservoirs.