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

There exists differential swelling during the pure and competitive adsorption of CO 2 -CH 4, whose mechanism was of broad interest to CO 2 -ESGR (CO 2 enhanced shale gas recovery) and CCUS (carbon capture, utilization, and storage) engineering. However, the kerogen differential swelling during CO 2 -CH 4 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 CO 2, pure CH 4, and a binary mixture of CO 2 + CH 4 (mole ratio = 1:1) gradually increase with the increasing temperature, pressure, and bulk mole of CO 2 . The activation energy of swelling deformation can be calculated via the Arrhenius formula, where they were 1.58 and 1.33 kJ/mol for CO 2 and CH 4, respectively, at 0.1 MPa, indicating that the swelling deformation of CO 2 adsorption requires more energy to trigger than CH 4 . CO 2 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 CO 2 -ESGR.