Thermodynamics and Kinetics of CO2/CH4 Adsorption on Shale from China: Measurements and Modeling

Abstract

CO2-enhanced shale gas recovery (CO2-ESGR) sequestrates anthropogenic CO2 and improves the profitability of shale gas exploitation. This work investigated the adsorption behaviors of CO2 and CH4 on shale from China at 20, 40, 60 and 80 °C. The pressure ranges for CO2 and CH4 were 1–5 and 1–15 MPa, respectively. The excess adsorbed amount of CH4 increased with increasing pressure from the beginning to the end, while the maximum excess CO2 adsorption was observed at approximately 4 MPa. The absolute average deviations (AADs) of CO2 and CH4, determined by the Langmuir + k model, were 2.12–3.10% and 0.88–1.11%, respectively. Relatively good adsorptivity for CO2 was exhibited when the pressure was less than 5 MPa, which was beneficial to the implementation of CO2-ESGR. With continuous increases in pressure, the adsorption capacity of CO2 was weaker than that of CH4, suggesting that the injected CO2 would reduce the partial pressure of CH4 for CO2-ESGR and the displacement effect would no longer be significant. In addition, the adsorption rate of CO2 was much faster than that of CH4. CO2 was more active in the competitive adsorption and it was advantageous to the efficiency of CO2-ESGR.