Adsorption-induced permeability change of porous material: a micromechanical model and its applications

This study focuses on developing a micromechanical model of poroelasticity with adsorption-induced permeability change occurred in porous material. The underlying pore pressure was represented by means of virial expansion to evaluate such adsorption-induced permeability change, in which the solid-gas interactions or the effects of interactions between molecules were involved. The relation between surface strain and volumetric strain under infinitesimal deformation conditions was presented to gain an explicit formulation of pore surface area with respect to volumetric strain and porosity. After the formulation of surface stress modified by Langmuir isothermal adsorption was derived, the differential micromechanical constitutive model of porous material was obtained. By providing that the ratio of current permeability to initial one was equal to the cubic ratio of current porosity to initial porosity, the differential equations for permeability change was consequently obtained. The present simulations showed that the predictions from the model are in good agreement with the experimental results of permeability change of coal induced by adsorption of CO and CH under confined pressure conditions in the literature.