Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

An extensive lab. program was conducted for the measurement of the interfacial tension between CO2 and water or brine covering the ranges of (2 to 27) MPa pressure, (20 to 125)C temp., and (0 to 334 010) mg/L-1 water salinity. The lab. expts. were conducted using the pendant drop method combined with the soln. of the Laplace equation for capillarity for the profile of the brine drop in the CO2-brine equil. environment. The anal. of the resulting set of 378 IFT measurements reveals that: (1) under conditions of const. temp. and water salinity, IFT steeply decreases with increasing pressure in the range P < Pc and mildly decreases for P > Pc with an asymptotic trend toward a const. value at higher pressures; (2) under the same conditions of const. pressure and temp., IFT increases with increasing water salinity, reflecting decreasing CO2 soly. in brine as salinity increases; (3) the dependence of IFT on temp. is more complex than that on either pressure or salinity, depending on the CO2 phase. For T < Tc, IFT increases with increasing temp., and around the crit. point (T ~ Tc), IFT significantly decreases (believed to be assocd. with the fact that at Tc the IFT between CO2 liq. and vapor phases tends to zero) and then increases again with increasing temp. for T > Tc with an asymptotic trend toward a const. value for high temps. The dependence of IFT on pressure, temp., and water salinity for CO2 and water/brine systems can be well approximated by a power function of pressure whose coeff. and exponent depend on temp. and water salinity. These results indicate that, in the case of CO2 storage in deep saline aquifers as a climate-change mitigation strategy, the formation water displacement by injected CO2 during the injection (drainage) phase of CO2 storage and the possible subsequent CO2 displacement by invading brine during the CO2 migration (imbibition) phase depend on in situ conditions of pressure, temp., and water salinity through the effects that these primary variables have on the IFT between CO2 and aquifer brine.