(303e) Determining Wettability of CO2/Water/Mineral Systems with Monte Carlo Molecular Simulations

Geological sequestration is recognized as a potential method for the reduction of carbon dioxide emissions.  A deep understanding of the interactions between the fluid CO₂-rich and water-rich phases and the caprock mineral of a sequestration site is necessary for the estimation of that site's ability to store CO2 safely.  In particular, changes in wettability accompanying changes in reservoir temperature and pressure could alter the sealing efficiency of the caprock, which is defined by the capillary breakthrough pressure.  The breakthrough pressure, in turn, depends on the CO₂/water/mineral contact angle and the interfacial tension between the water-rich phase that saturates caprock pores and the CO₂-rich phase present in the reservoir.  We present here the use of Monte Carlo methods to measure the interfacial tension and contact angles of CO₂/water mixtures over model silica and phyllosilicate surfaces.  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 values.