Nanofluid Enhanced Oil Recovery Using Hydrophobically Associative Zwitterionic Polymer-Coated Silica Nanoparticles

Intense interest has been shown in the development of “smart nanofluids” because they can dramatically change their flow properties in complex fluid systems. We introduce a robust and straightforward approach to develop a smart nanofluid system, in which associative silica nanoparticles (ASNPs) were incorporated to regulate their flow properties in rock pores. ASNPs were synthesized by covalently coating a hydrophobically associative hygroscopic zwitterionic poly[2-methacryloyloxyethyl phosphorylcholine (MPC)-co-divinylbenzene (DVB)] shell layer on 20 nm sized silica nanoparticles (NPs) by surface-mediated living radical polymerization. The essence of our approach is to copolymerize DVB, which endows the polymer shell of ASNPs with a weak long-range hydrophobic attraction. This leads to the favorable formation of a wedge film as a result of structural disjoining pressure. This wedge film made the oil adsorbed on the rock surface more dewettable, thus enhancing the efficiency of oil recovery. As a result of this unique behavior, the ASNP nanofluid developed in this study remarkably improved the fluidity of complex oil fluids; ∼5 vol % oil recovery enhancement and ∼0.3 psi pressure reduction were also achieved in comparison to neat nanofluid controls.