Molecular dynamics of methane adsorption in shale

Abstract

In this paper, the supercritical gas molecule adsorption characteristics of methane in shale are quantitatively described by using the lattice theory. The results show that the methane adsorption capacity predicted by this theory is high, with the average absolute error 0.003 3 mmol·g−1. There is a near-linear positive relationship between the adsorption potential between methane and the solid surface (ϵs) and the experimental temperature. The value of the average potential between the adsorbate molecules (ϵa) is distributed in −0.841–1.791 kJ·mol−1, and the absolute value of ϵa is significantly smaller than the absolute value of ϵs, indicats that the potential energy between the adsorbate molecules is significantly smaller than that between the adsorbate molecules and the pore surface of shale. When the temperature is relatively low (T = 308.55 K), the value of ϵs/ϵa is 7.5 times; with the increases of the temperature, the magnification will gradually decrease and keep stabilize (3.37 times).