Injection of supercritical carbon dioxide into underground geological formations is considered as an attractive approach for long-term anthropogenic carbon storage and enhanced gas and oil recovery. In a stimulated shale reservoir, carbon dioxide plume displaces innate fluids in hydraulic and natural fractures and matrix pores. In particular, enhanced natural gas recovery can be achieved through competitive sorption of carbon dioxide and methane sorbed on clay mineral surfaces in the pore and fracture walls. Characterization of carbon dioxide and methane interaction with clay minerals is mandatory to reliably determine gas storage and release in shales and predict reservoir performance.<br/>Molecular dynamics and Monte Carlo simulations were carried out to investigate sorption behavior of carbon dioxide and methane mixtures on illitic clay surfaces in dry shales. Various compositions of the mixtures and distributions of isomorphic substitutions in clay layers were chosen to explore competitive sorption depending on component concentration and charge localization. The simulations show that carbon dioxide is preferentially sorbed on the illitic surface and is capable to promote methane desorption. Density distributions of the molecular species in pore space reveal formation of multilayers on the clay surfaces at elevated pressures. Mixed sorption isotherms were compared with sorption isotherms of pure compounds and thermodynamic quantities were reported to characterize the interaction of the binary carbon dioxide / methane mixture with the clay surface.

Molecular simulations of competitive sorption of carbon dioxide and methane on illitic clay surfaces in shales

255th National Meeting (2018)

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