(37i) Calculating the Interfacial Properties of CO2/Water/Silica Systems Using Monte Carlo Molecular Simulations

Geological sequestration has the potential to occupy a strategic role in the reduction of carbon dioxide emissions. Before injecting CO₂ into a potential storage site, one must first assess the capability of the site to retain the injected CO₂. Understanding the interactions between the fluid CO₂-rich and water-rich phases and the caprock mineral of a site is particularly important. These interactionsâ??in the form of the CO₂/water/caprock contact angle and CO₂/water interfacial tensionâ??dictate the breakthrough pressure, that is, the pressure at which the CO₂-rich phase may leak due to capillary failure. We present here the use of Monte Carlo methods to measure the interfacial tension and contact angles of CO₂/water mixtures near a silica surface. We apply a combination of interface potential free energy techniques and expanded ensemble simulations to measure differences in these interfacial properties over a range of temperature and pressure conditions for several combinations of available water and CO₂ molecular models.