Molecular dynamics simulations of the enhanced recovery of confined methane with carbon dioxide

Abstract

For the first time, the enhanced recovery of confined methane (CH₄) with carbon dioxide (CO₂) is investigated through molecular dynamics simulations. The adsorption energy and configuration of CH₄ and CO₂ on the carbon surface were compared, which shows that CO₂ is a good candidate in displacing confined CH₄. The energy barrier required for displacing CH₄ by CO₂ injection was found to depend on the displacement angle. When CO₂ approached vertically to the carbon surface, the displacement of CH₄ occurred most easily. The curvature and size effects of the carbon nanopores on CH₄ recovery were revealed and indicated that there exists an optimum pore size making the displacement occur most efficiently. The underlying mechanisms of these phenomena were uncovered. Our findings and related analyses may help to understand CO₂ enhanced gas recovery from the atomic level and assist the future design in engineering.