Wettability of Supercritical CO2–Brine–Mineral: The Effects of Ion Type and Salinity

Abstract

Deep saline aquifers are considered as perfect storage sites to sequestrate CO2. Interfacial tensions (IFTs) and contact angles (CAs) are key parameters in the heat and mass transfer processes for CO2/brine/mineral systems in porous media. In the present study, a molecular dynamics simulation method was used to investigate the effects of brine salinity and ion type on wettability of CO2/brine/mineral systems at 20 MPa and 318.15 K. Four common brines were selected as NaCl, KCl, CaCl2, and MgCl2. Interfacial tensions, water contact angles, and hydrogen bond structure and dynamics have been analyzed. The effects of brine salinity and ion type on water contact angles were found to be very complicated. For MgCl2 and NaCl solutions, the contact angle increases with salinity. For CaCl2 and KCl solutions, contact angle first increases and then remains constant with salinity. The product of IFT(CO2–brine) and the cosine of CA was found to be constant for all brine solutions studied. In the context of large uncert...