Water film rupture caused by supercritical CO2 bubbles under geologic sequestration conditions: A molecular dynamics simulation study by driving bubbles with different forces

Wettability is one of the key factors that govern supercritical CO2 migration in porous media under geologic sequestration conditions. Supercritical CO2 adhesion on mineral surfaces has been found which greatly enlarge water contact angles of CO2/brine/mineral systems. Supercritical CO2 adhesion on mineral surfaces was found to happen: (1) when generating CO2 bubbles repeatedly to measure contact angles of CO2/brine/mineral systems by a pendant CO2 droplet method (Wang et al., 2013); or (2) during CO2 receding process when measuring dynamic contact angles by a captive CO2 droplet method (Zhang et al., 2016). Supercritical CO2 adhesion happens repeatedly with a certain possibility, the increase of water contact angles is unlikely to be caused by surface functional groups variation at least it is not the only reason. As a result, the water film between a supercritical CO2 bubble and the mineral surface plays an important role in supercritical CO2 adhesion. In this paper, molecular dynamic simulations have been used to predict the film rupture process on mineral surfaces under geologic CO2 sequestration. Different forces have been imposed on all molecules in the supercritical CO2 bubble and the variation of CO2/brine/mineral configuration has been analysed. This study can improve our understanding of supercritical CO2 adhesion as well as film stability theory.