Previous studies on Nanoparticles (NPs) application for Enhanced Oil Recovery (EOR) methods have revealed their effective role in the rock wettability alteration, relative Interfacial Tension (IFT) and oil viscosity reduction, formation and stabilization of the emulsions, and reduced asphaltene precipitation, which are all in direct relationship with oil/water interfacial properties. This study focuses on the interfacial properties of oil/water in the presence of Titania NPs and different ions at different pressures and temperatures. For this, different concentrations of TiO2 NPs in the Formation Water (FW) were prepared to monitor the effects of NPs on the oil/water IFT, carbonate rock wettability, zeta potential, and asphaltene adsorption. The results on IFT values indicated that NPs behavior at high pressures and temperatures is completely different, as compared to the ambient conditions, and 1000 ppm NPs introduced the lowest IFT at 600 psi and 60 °C. This reduction is potentially attributed to the asphaltene adsorption at the oil/water interface by TiO2 NPs, which hinders the asphaltene deposition at the interface and in turn IFT increasing. Contact angle results revealed two distinctive behaviors for NPs at high and low concentrations. In other words, with the first interval (below the optimum concentration), an increase in NPs concentration led to a quick wettability alteration toward the water-wet condition, and with the second one (above the optimum concentration), there was an increase in contact angle with an increase in NPs concentration, which is due to the NPs stacking near the rock surface. These results were in good accordance with zeta potential measurements, in which 1000 ppm nanofluid presented the highest stability (zeta potential value of −46.9 mV). Batch adsorption experiments resulted that catalytic TiO2 NPs are capable of adsorbing asphaltene at the oil/water interface. In addition, the results on fitting experimental data to the Langmuir and Freundlich Isotherms showed that the adsorption best fitted Langmuir Isotherm and hence the adsorption type is a monolayer.
Surfactant mixtures at the oil–water interface
