Interfacial Tensions between Reservoir Brine and CO2 at High Pressures for Different Salinity

Abstract

In this paper, an experimental technique has been developed to study the interfacial interactions of the reservoir brine and CO2 system at high pressures and elevated temperatures. Using the axisymmetric drop shape analysis (ADSA) for the pendant drop case, this new technique makes it possible to determine the interfacial tension (IFT) and visualize the interfacial interactions phenomenon between the reservoir brine and CO2 under practical reservoir conditions. The laboratory experiments were conducted for the measurement of the IFT between CO2 and pure water or brine covering three interesting salinities (0 mg/L, 14224.2 mg/L and 21460.6 mg/L). Comparing the data of the CO2−pure water interfacial tension with other papers at 45 °C, at low pressures ( 7.38 MPa), all data have slight deviations. The dynamic and equilibrium IFT are measured as a function of pressure at the stratum temperature (97.53 °C). It is found that the dynamic IFT gradually approaches to a constant value, which is the equilibrium IFT. The equilibrium IFT decreases as the pressure increases but increases as the salinity increases. In addition, the wettability of the reservoir brine and CO2 system changes from the hydrophilic case to the hydrophobic case as the pressure increases, and the same phenomenon decreases as the salinity of brine increases.