Molecular simulation of CO2/CH4 competitive adsorption in kerogen

Key words:  kerogen  competitive adsorption  molecular simulation  volumetric strain

Abstract:

The kerogen model was built and the organic matter was selected as the research object. The CH₄ and CO₂ adsorption behavior and the associated volumetric strain of the kerogen at different CO₂ mole fractions and different pressures were investigated using Monte Carlo (GCMC) and Molecular Dynamic methods. The results show that the adsorption amount of CH₄ and CO₂ increases with pressure increase. And CO₂ adsorption amount can reach maximum at lower pressure. The adsorption of CH₄ and CO₂ accords with the law of Langmuir adsorption and can be fitted by Langmuir equation. The adsorption selectivity of CH₄/CO₂ decreases as the CO₂ mole fractions increase at the same pressure and temperature, and the CO₂ is easier adsorptive by kerogen. Also it is found that there is a strong interaction between kerogen and CO₂, and different atoms play different roles for adsorption in kerogen. At low pressures, the adsorption is the main reasons for volumetric strain, and at high pressures, the pressure is a significant role in volumetric strain.