Impact of organic solutes on capillary phenomena in water-CO-quartz systems.

Hypothesis: The migration of supercritical CO (scCO) injected into underground reservoirs as part of carbon capture and storage is influenced by organic contamination affecting mineral wettability. Molecular dynamics (MD) simulations of relevant systems that incorporate representative organic solutes allow detailed investigation of changes in fundamental interfacial and capillary properties.

Experiments: We use MD simulations to explore the effects of four organic solutes (quinoline, decanoic acid, coronene, sorgoleone) on the wettability of quartz by water in the presence of scCO. We examine the impacts of polar, alkyl, and aromatic moieties as well as fluid flow velocity at elevated temperatures and pressures.

Findings: Organic molecules accumulate at the water-CO interface, where they distribute according to their size and functional groups. Certain organics penetrate the adsorbed water film at the quartz-CO interface, revealing two modes of hydrogen bonding between polar organic functional group, water, and quartz surface -OH groups. Interfacial energies and contact angles are minimally impacted by organic adsorption at the water-CO interface, possibly due to simultaneous CO desorption. Non-equilibrium MD simulations reveal that flow-induced redistribution of organic compounds modulates the radii of curvature of the advancing and receding water-CO interfaces. Our results indicate that organic adsorption on water surfaces is likely ubiquitous during multi-phase flow in soils and sedimentary rocks, with implications for the mobilization and transport of organic compounds.