Study of the impact of high temperatures and pressures on the equilibrium densities and interfacial tension of the carbon dioxide/water system

The development of successful and economical CO₂ geological storage projects requires a precise estimation of the saturated phase densities and interfacial tension of the CO₂/H₂O system. The axisymmetric drop shape analysis (ADSA) method was used for measuring the interfacial tension of this system at temperatures over the range (298 to 469) K and pressures up to 69 MPa. The phase densities, required to determine accurate IFT values, were determined by measuring the oscillation period of the equilibrated phases with an Anton Paar densitometer. A correlation to readily determine the density of the CO₂-saturated water phase in the range of interest is proposed and the use of pure compound densities for the calculation of the interfacial tension values discussed. The Cubic-Plus-Association equation of state (CPA EoS) was used to estimate the phase behaviour pressure and temperature dependence of the system studied with very good results. Bulk phase properties and influence parameters adjusted to pure compounds surface tensions within the density gradient theory (DGT) were used to predict the CO₂/H₂O interfacial tensions with remarkably low deviations from the measured values.