Characterization of reservoir systems at elevated pressure

The efficiency in enhanced oil recovery strongly depends on interphase behaviour of the participating fluids and solids. Analysis is carried out using experimental techniques for recording contact angles and interfacial tension at elevated pressure and relating these data by use of known approaches from literature. Even in fairly incompressible liquid–liquid–solid systems the solid–liquid interfacial energies are shown to change at rising pressure. Combination of measured contact angles of a ternary water–n–alkane–dolomite system with those of the respective binary systems enables estimation of surface and interfacial energies of rock surfaces. In the presence of gases, especially methane, the water–n-alkane interfacial tension as well as the contact angle of a (non-wetting) water drop on dolomite in n-alkane is decreased which is only possible if the interfacial energy of n-alkane–dolomite rises based on Young's law. In a water-wet system, wetting by water was also observed to improve under pressure which is attributed to a decreasing water–rock interfacial energy since the water–oil interfacial tension is increased at the same time.