Molecular-scale insights into nanoconfined water-CO2 interactions in geological carbon storage

Abstract

Understanding the nanoconfined water-CO2 interactions at the molecular scale is of great importance for the fluid transport in confined porous media. Here, a series typical water film and water bridge scenarios are determined, and the associated impacts on nanoconfined water-CO2 interactions as well as the geological hydrocarbon recovery and CO2 storage are investigated in nanopores. Our results confirm either in water film or water bridge scenarios, the competitive adsorptions of nanoconfined water and CO2 reduce the adsorbed water amount and derive the new water bridge with CO2 additions. Such a phenomenon indicates the substrate surface shifts from water-wet to partially CO2-wet, with lower fluid molecule diffusions and illite-water-CO2 sandwich-structured adsorption layer. Overall, our work investigates the mechanism of CO2 effects on distributions and aggregations of nanoconfined water molecules in nanopores, which also provides molecular-scale insights into the nanoconfined water-CO2 interactions in the processes of geological CO2 storage and utilization.