Adsorption and selectivity of CH4/CO2 in functional group rich organic shales

Abstract

The exploration of shale gas resources has been increasing rapidly in the past decades owing to the growing demands for resources and environmental protection. In this work, we construct a series of functional group rich organic (FGRO) shale models. The shale gas capacity, sequestration amount of CO2 and selectivity of CO2/CH4 in these organic-rich shales are explored by molecular simulation. It is found that the shale gas capacities in the FGRO shale models are smaller than that in pristine pillared shale model owing to the excluded volume effect of organic matter. However, the FGRO organic matter shows a significant effect on the selectivity of CO2/CH4. In particular, the selectivity of CO2/CH4 in the epoxy group rich organic (EGRO) shale model reaches 8.36, which is 3.73 times of that in pristine model without organic matter. Therefore, the EGRO shale may be a potential reservoir for sequestration of CO2. Meantime, by exploring the effects of geological depth on exploitation of shale gas or sequestration of CO2, an optimum depth of 1 km is recommended. It is expected that this work provides useful guidance for exploitation of shale gas and sequestration of CO2.