The injection of supercritical CO2 into deep saline aquifers has emerged as one of the most promising options to manage CO2 emission and sequestration. The interfacial tension (IFT) between supercritical CO2 and brine is an important contribution to the sequestration efficiency. In turn, the IFT is a complex function of the brine phase composition, concentration of each brine component, salt type, and environmental conditions (i.e., temperature and pressure). Molecular dynamics simulations can be used to probe the dependence of the IFT on these factors. Here, we focus on NaCl and CaCl2 (two common salts found in saline aquifers), and employ KCl and MgCl2 to carry out additional study. We examine the contribution of ions to the IFT increase (??) relative to the CO2�pure liquid water system, including cation charges, atomic parameters (mass, Lennard-Jones parameters s, and e), and ionic strength, at typical reservoir conditions (temperature of 343 K and pressure of 20 MPa), and 0.9 to 2.7 mol/L water salinity. We note that the cation valence is the leading contributor to the observed increases in IFT's. The trends of deeper potential well gives higher ?? can be clearly observed. Mass is the minor reason to the ??. The ?? is linear relationships with the salts ionic strength. The slope of ?? vs. ionic strength for the CO2/CaCl2 solution is similar with the corresponding one of the CO2/NaCl solution. It is totally different from the ?? vs. salinity curves, which increasing slope for the CO2/CaCl2 solution is more than two times larger than that for the CO2/NaCl solution. The IFT induced by ionic strength, for solutions containing CaCl2 is similar with that of solutions containing NaCl, at a given ionic strength. This provides a new sight to understand and predict IFT of aqueous, ion containing, two-phase interfacial systems under pressure.

Effects of salts on the interfacial tension at the supercritical CO<sub>2</sub>�brine interface

248th National Meeting (2014)

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Effects of salts on the interfacial tension at the supercritical CO2�brine interface

Effects of salts on the interfacial tension at the supercritical CO₂�brine interface