Interfacial Tension and Wettability Change Phenomena during Alkali–Surfactant Interactions with Acidic Heavy Crude Oil

In this work, a newly formulated sulfonate-based surfactant and two other commercial sulfate-based surfactants with the capability of tolerating harsh underground reservoir conditions, such as high-saline formation water and high temperature, were prepared. Sodium metaborate as an effective alkali compound was also used to provide alkali–surfactant combination. Interfacial tension (IFT) measurements as well as wettability examinations for different salinities and mixture conditions were performed for an extended range of the chemical concentrations. The wettability tests including both contact angle measurements and Amott cell tests were performed on saturated Berea sandstone plug samples and rock slices, while the precise spinning drop technique was used for IFT measurements. The mixtures of both surfactant groups and alkali resulted in a minimum IFT value required to attain an optimum three-phase region at high-salinity conditions. The addition of the alkali to the surfactant solution reduced the lowest...