Phase Diagram and Interfacial Tensions of Brine-Dodecane-Pentanol-Sodium Octylbenzenesulfonate System

Abstract

This system has been chosen as a typical model in the frame of research on microemulsions and their use in tertiary oil recovery.The phase diagrams of such systems present one-phase, two-phase, three-phase regions. The needs of tertiary oil recovery lead to try to find out active mixtures (surfactants and cosurfactants) able to dissolve large amounts of oil and water and to achieve low interfacial tensions. The very low interfacial tensions are generally observed on three-phase states such as an intermediary (middle) phase (m) is in equilibrium with an aqueous phase (w) and an organic phase (o). Such states are called of Winsor’s type III. It exists conditions to observe the equality of interfacial tensions γ_mw and γ _mo; these conditions have been termed optimal (see e.g. 1–7).