Oil recovery mechanisms of Pickering nanoemulsions stabilized by surfactant-polymer-nanoparticle assemblies: A versatile surface energies' approach

In this article, we present a holistic approach to predict the interfacial activity of surfactant/polymer/nanoparticle stabilized Pickering nanoemulsions. Dynamic interfacial tension was measured and their profiles were generated in real time using pendant drop technique. The free detachment energies (E-det) at liquid-liquid interface decreased with time owing to gradual slipping of emulsifier(s) toward oleic phase, which translates to favorable oil displacement. Crude oil miscibility experiments confirmed synergistic influences of gemini surfactant, partially hydrolyzed polymer and silica nanoparticles. However, it was recognized that these investigations do not consider effects of rock mineralogy and solid-liquid dynamics, and hence, must be replaced with an evolved surface wetting approach. A "modified" Arrhenius model is tailor-made for nanoemulsions (as oil displacing fluids) to determine the surface activation energies and mechanistically discuss the altered wettability state of reservoir rock(s). Surfactant-polymer-nanoparticle (SPN) nanoemulsion exhibited enhanced oil displacement as compared to surfactant-stabilized and surfactant-polymer stabilized nanoemulsions. In summary, the surface energy approach was corroborated from theoretical as well as experimental investigations. Qualitative investigation of SPN nanoemulsion-based oil displacement was performed via microscopic imaging, infrared spectroscopy and wettability alteration technique by mimicking different flooding stages in oil-saturated reservoir models for application in enhanced oil recovery (EOR).