Study concerning the supercritical adsorption behavior of shale gas that analyzed different adsorption mechanisms

Owing to the gradual depletion of easily accessible mineable resources, deep mining has now become standard practice. In deep shale gas reservoirs, a substantial level of the total shale gas resource is obtained from adsorbed methane. Moreover, methane adsorption in deep shale gas reserves has been defined as supercritical adsorption. The effect of high temperature and high pressure on the adsorption capacity of methane has become more critical. Shale possesses an unmistakably multi-scale pore structure, whose adsorption mechanisms differ in pores of different sizes. Therefore, it was considered necessary to understand precisely the supercritical adsorption behavior of shale gas under different adsorption mechanisms. To this end, a supercritical weighted adsorption model for shale gas, that analyzed micropore-filling with a mesoporous monolayer surface was developed. Based on this model, this research analyzed the adsorption and thermodynamic characteristics of shale gas at different temperature and pressure levels. The effects of the weighting factors on shale's adsorption properties, pore fractal dimensions and thermodynamic parameters have also been discussed. The study's results revealed a significant negative correlation between methane adsorption and temperature. Furthermore, there was a consistent increase in the isosteric heat of adsorption and a corresponding decrease in the standard entropy of adsorption under increasing adsorption. Absolute adsorption tended to increase following an increased weighting factor. Upon an analysis of shale's pore structure characteristics, a positive correlation between the fractal dimension and the weighting factor was discovered. With regard to the thermodynamic parameters, the isosteric heat of adsorption rose as the weighting factor increased, while the standard entropy of adsorption tended to decrease. The research findings have established a theoretical basis for evaluating deep shale gas reserves.