Kerogen Differential Swelling during CO2-CH4 Adsorption: Mechanism and Significance

Abstract

There exists differential swelling during the pure and competitive adsorption of CO2-CH4, whose mechanism was of broad interest to CO2-ESGR (CO2 enhanced shale gas recovery) and CCUS (carbon capture, utilization, and storage) engineering. However, the kerogen differential swelling during CO2-CH4 adsorption has been rarely reported, and so is its mechanism and significance. Here, the differential swelling mechanism of kerogen atomic representation was investigated using molecular simulation and the poromechanical model. Results indicated that swelling ratios for the systems of pure CO2, pure CH4, and a binary mixture of CO2 + CH4 (mole ratio = 1:1) gradually increase with the increasing temperature, pressure, and bulk mole of CO2. The activation energy of swelling deformation can be calculated via the Arrhenius formula, where they were 1.58 and 1.33 kJ/mol for CO2 and CH4, respectively, at 0.1 MPa, indicating that the swelling deformation of CO2 adsorption requires more energy to trigger than CH4. CO2 plays a dominant role in triggering the swelling deformation of competitive adsorption system. The swelling activation energy of pressure dependence firstly increases and then decreases with the increasing pressure. The outcomes of this paper have a higher fidelity than many previous efforts and were expected to be of broad interest to CCUS and CO2-ESGR.