Methane Adsorption on Carbon Models of the Organic Matter of Organic-Rich Shales

Abstract

The organic matter in organic-rich shales has an important significance for the methane adsorption capacity on shales. Kerogen is simplified to ideal graphite, and oxygenated functional groups are grafted onto graphite surfaces to obtain different O/C atomic ratios, reflecting varying maturation levels of kerogen. The adsorption behaviors of methane in the pores of graphite with different O/C ratios were investigated by the grand canonical Monte Carlo method. The results show that the isosteric heat of adsorption of methane is reduced with an increase in the pore size or a decrease in the O/C ratio. The methane adsorption capacity in micropores increases with an increasing pore size, whereas it decreases with an increasing pore size in mesopores. The methane adsorption capacity in pores with the same pore size decreases with decreasing O/C ratio. The proportion of the adsorbed gas in the pores decreases either with increasing pressure with the same pore size or with an increasing pore size under the same ...