Low-energy emulsification of oil-in-water emulsions with self-regulating mobility via a nanoparticle surfactant

Oil-field chemists and engineers have searched a method for intelligent flooding of chemical-intervention-based processes with self-regulating mobility in subterranean areas for decades. By designing hydrophilic nanoparticles (amine-terminated nanosilica particles (ATNPs)) and nonionic surfactant laurel monoanolamide (LEMA) molecules with complementary hydrogen bonding functionalities that bind one another at the oil-water interface, we developed a route to in situ oil-in-water (O/W) emulsions without a phase inversion point. Apparent viscosities of the O/W emulsions demonstrated a negative relationship to oil saturation and a positive relationship to water saturation over a broad range of water saturations from 30 to 78%. These emulsions are produced by low-energy emulsification, simply accomplished by mild shaking for tens of seconds. The total concentration of the nanoparticle surfactant is 7000 mg/L, much lower than reported in the previous literature. We show that a local turbulent eddy of the immiscible fluids provides sufficient energy and time for the nanoparticle surfactant to create O/W emulsions since their morphology, droplet size distribution, rheology, and stability are similar to those produced by high-energy emulsification using a high-shear rotor stator mixer. Emulsification kinetics and physical model tests demonstrate the synergistic effect of ATNPs and LEMA on arresting Ostwald ripening, increasing capillary numbers, and self-controlling the displacement frontier of these emulsions. This system produced a high oil recovery efficiency of a three-layer heterogeneous square core with an incremental oil recovery factor of 33.7% original oil in place (OOIP) and an ultimate recovery factor of 72.1% OOIP when the water cut of the earlier water flooding exceeds 98%. This work paves a pathway to the production of smart in situ O/W emulsions using nanoparticle surfactants for industrial oil recovery applications.