Polyacrylamide microgel nanospheres were synthesized by inverse microemulsion polymerization with redox initiators on the basis of the preparation of water-in-oil (W/O) microemulsion with diesel oil, sorbitan monooleate, polyethylene glycol sorbitan monostearate, acrylamide, N,N′-methylenebisacrylamide and deionized water. By adopting a twice synthesis process, polymer content can be substantially lifted from 24.43 wt% to 35.04 wt%. Moreover, it's proved that nanospheres can expand from the initial 50nm or so to several microns after water absorption.

In this paper, synergy effects of the emulsifiers (sorbitan monooleate and polyethylene glycol sorbitan monostearate) separately with alkalis and surfactants are firstly proposed and verified via the achievement of ultra-low interfacial tension (IFT). Profile control and oil displacement tests by sandpacks further demonstrated the promising future of nanospheres in enhanced oil recovery (EOR) with incremental oil recovery over 20% OOIP after primary recovery.

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