Microscale transport of CO_{2} and H_{2} storage in shale gas formations.

Abstract

This work focuses on microscale transport behavior of binary mixtures in the context of CO_{2} and H_{2} storage in shale gas formations. To this end, a multiple relaxation time lattice Boltzmann (LB) model is implemented to simulate microscale transport behavior. In the LB model, a combined boundary scheme of bounce-back and specular reflection is used to model fluid-wall interactions and slippage effect, and a regularization algorithm is used to obtain accurate solutions for complex geometries. The binary LB model is validated using the Kramer problem and pseudobinary flows in slit and irregular nanopores. Subsequently, pressure-driven flows of CH_{4}-CO_{2} and CH_{4}-H_{2} binary mixtures are investigated in slit nanopores and irregular porous media under various pressure and composition conditions. The impact of simulation conditions on fluid velocity, mass flux, apparent permeability, Péclet number, and pressure drop is comprehensively examined. The dynamics of CO_{2} and H_{2} displacing CH_{4} in nanoconfined spaces are studied. The results point to different displacement mechanisms between CO_{2} and H_{2} due to their different molecular properties. In summary, this work provides deep insights relevant to subsurface storage of CO_{2} and H_{2} in shale gas reservoirs.