A Pore-Network Simulation Model of Dynamic CO2 Migration in Organic-Rich Shale Formations

One attractive aspect of CO 2 sequestration in shale formations is the preferential adsorption of CO 2 compared to methane, which may provide enhanced methane production as well as sequestration of carbon dioxide. In this work, a comprehensive theoretical model of CO 2 migration at the pore scale is developed to study CO 2 migration properties in organic-rich shale formations. The proposed model takes into account dynamic competitive adsorption between CO 2 and CH 4 , slip-flow effects due to the nanometer range of pore sizes, and pore-size changes due to adsorption. Because of the high pressure and temperature, the injected CO 2 is in supercritical phase. Pore bodies in the shale matrix are irregular in shape, with roughness along pore wall. The structure of pore body affects the amount of surface areas and associated number of adsorption sites, and hence, a shape factor is proposed in this work to consider the irregularity of pore structure in shale matrix. The sorption of CO 2 leads to an apparent retardation of the migration of CO 2 , which is quantified in this work. The developed pore-network model is extended to consider the impacts of different spatial distributions of the organic materials within the shale matrix.