Synergistic and Antagonistic Effects of Silica-based Nanofluids and Surfactant on the Dynamic and Equilibrium Interfacial Behavior of Light, Intermediate and Heavy Crude Oils at Oil-aqueous Interfaces

Lingyun Bai, Clemson University


In order to more efficiently exploit petroleum reservoirs, there needs to be an understanding of how to mobilize crude oils from their reservoirs. We explored the ability of silicon dioxide nanoparticles (SiO2 NPs) to improve the efficiency of the chemical-enhanced oil recovery process (EOR) that uses surfactant flooding. We investigate how varying concentrations of SiO2 NPs (i.e., 0, 0.001, 0.005, 0.01, 0.05, and 0.1 wt%) and Tween®20, a nonionic surfactant, at 0, 0.5 and 2 critical micelle concentration (CMC) impact the stability of nanofluids and alter the interfacial tension (IFT) at the oil-aqueous interface for 5 wt% brine-surfactant-SiO2 nanofluid-oil systems for West Texas Intermediate light crude oil, Prudhoe Bay medium crude oil, and Lloydminster heavy crude oil. Nanofluid stability is monitored by dynamic examination of the size, zeta potential, and sedimentation of the particles in suspension. The interfacial property of the brine-surfactant-SiO2 nanofluid-oil systems was characterized by measuring the equilibrium and dynamic behavior of IFT. Our study demonstrates that SiO2 NPs may have no effect, decrease, or increase IFT of the brine-surfactant-oil systems. The constituents of the oil and aqueous substances impact the IFT behavior of brine-surfactant-oil systems, with the presence of nanoparticles leading to contrasting IFT trends according to the type of crude oil. For the light oil system (0.5 and 2 CMC Tween®20), IFT increases as a function of SiO2 NPs concentration. While a threshold concentration of SiO2 NPs was observed for the medium (0.5 and 2 CMC Tween®20) and heavy (2 CMC Tween®20) oil systems in terms of the IFT trends. Concentrations below the SiO2 NPs threshold concentration resulted in a decrease in IFT and concentrations above this threshold resulted in an increase in IFT. IFT decreases until NPs concentration reaches a threshold concentration where synergetic effects between nonionic surfactants and SiO2 NPs play a significant role. Adsorption of both SiO2 NPs and surfactants at an interface causes a synergistic effect and an increased reduction in IFT. Overall, the effectiveness of brine-surfactant-SiO2 nanofluids to decrease the IFT between the oil-aqueous phase for the three tested crude oils are ranked as: (1) Prudhoe Bay > (2) Lloydminster > (3) West Texas Intermediate. This ranking is impacted by the amount of asphaltenes and resins in the crude oils. IFT between the oil-aqueous phase of crude oils that contain the highest amount of asphaltenes and resins, which are Prudhoe Bay (14 wt%) and Lloydminster (10 wt%) were impacted by the brine-surfactant-SiO2 nanofluid. IFT between the oil-aqueous phase of crude oils with the lowest amount of asphaltenes and resins, that is West Texas Intermediate (7 wt%), were not impacted by the brine-surfactant-SiO2 nanofluid. It can be concluded that asphaltenes and resins are critical components of crude oils in the control of IFT of crude oil-surfactant-nanofluid systems. In conclusion, a decrease in IFT establishes the SiO2 NPs potential to decrease capillary pressure and induce the movement and recovery of oil in original water-wet reservoirs. An increase in IFT demonstrates the potential of SiO2 NPs to increase capillary pressure and increase oil recovery in reservoirs subject to wettability reversal to water-wet condition.