Nanoparticles have been systematically investigated for their EOR mechanisms, such as rock wettability alternation, oil displacement by disjoining pressure, and the stabilization of emulsion and foam. Nanogels are nano-sized crosslinked polymeric particles that have the properties of both nanoparticles and hydrogels. The goal of this study is to investigate the oil-water interfacial behavior in the presence of nanogels, especially the dynamic interfacial tension and the stability of oil-in-water (o/w) emulsions. The nanogels synthesized in this study are able to reduce the oil-water interfacial tension and stabilize the o/w emulsions. The diameter and zeta-potential of the charged nanogels are dramatically influenced by the brine salinity whereas the neutral charged nanogels are barely affected by salt. The synthesized nanogels are stable in distilled water and brines at room temperature for more than 60 days. The dynamic interfacial tension results show that the nanogels are able to reduce the oil-water interfacial tension to as much as 1/30 of the original value. In addition, the interfacial tension reduction is more significant at high salinity (ranging from 10,000 to 50,000 ppm NaCl concentration). Emulsion stability results demonstrated that the stability of emulsified oil drops was controlled by both the strength of the adsorbed nanogel layers and the interactions among oil drops. The salt dependent interfacial tension and emulsion stability indicated that the appropriate charged nanogel can be a promising candidate for enhanced oil recovery.

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