Mass Transfer between Crude Oil and Water. Part 2: Effect of Sodium Dodecyl Benzenesulfonate for Enhanced Oil Recovery

In enhanced oil recovery, synthetic surfactants are usually added to decrease the interfacial tension between oil and water. When alkaline are used, endogenous natural surfactants bearing acidic groups that can be found in acidic or heavy crude oils are activated in situ by ionization; they accumulate at the oilwater interface and reduce the interfacial tension. These crude oils are called interfacially reactive. In alkaline surfactant flooding, the interaction between synthetic surfactants and natural surfactants allows for the acquisition of ultralow interfacial tensions, lower than 103 mN/m. When reactive crude oils and water at different pH values are contacted, mass transfers of natural species (asphaltenes, naphthenic acids, etc.) from oil to water are observed. We report an experimental study of the influence of sodium dodecyl benzenesulfonate (SDBS) on mass transfer between oil and water phases, in which the final pH of the water phase was measured as a function of the SDBS concentration and initial pH. We also developed a model to account for the influence of the SDBS concentration on exchanges between the reactive crude oil and the aqueous phase. We found that the final pH of the water phase increases when the SDBS concentration increases, revealing a larger transfer of oil species into water. Finally, we show that a comparison between the mass transfer and interfacial tensions between crude oil and water allows for better insight into the interactions between synthetic and natural surfactants in alkaline surfactant flooding processes.