High-Performance Nanogel-in-Oils as Emulsion Evolution Controller for Displacement Enhancement in Porous Media

We designed and synthesized high-performance nanogel-in-oils with intermediate properties between solid particles and liquid droplets for multiphase flow control in porous media. The ultrasmall polymeric nanogels prepared via inverse emulsion polymerization were efficiently encapsulated in micrometer-sized oil droplets with the aid of surfactants during transfer from the oil phase to the aqueous phase. The composite colloidal system exhibited high loading capacity, unimodal size distribution, and long-term kinetic stability in suspension. The colloidal behaviors of nanogel-in-oils and the corresponding interfacial evolution during displacement in porous media were investigated via microfluidic experiments. In situ emulsification was observed with a state contrary to that of static characterizations. The spontaneous and sustainable formation of foam-like water-in-oil macroemulsions originated from aqueous phase breakup and oil film development, both enhanced by nanogel-in-oils. Sweeping efficiency enhancement by invasion events and residual oil transport in macroemulsion phases yielded exceptional displacement performances. Flow field fluctuations and emulsion state variations can be manipulated by adjusting nanogel-in-oil concentrations. The nanogel-in-oil suspension was found to exhibit optimal performance among the tested dispersed systems.