Regular nanogels have been demonstrated their inefficiency for subterranean oil recovery due to their intrinsic drawbacks of fast swelling within minutes, thermal instability, and salinity vulnerability. Prior deployment of swelling delayed nanogels mainly depended on the reservoirs at a relatively higher temperature. To address the issues encountered during engineering deployment, hereinwe devised an integrative approach to in situ form swelling delayed robust nanogels by introducing radically active monomers with thermally sensitive moieties. The nanoparticles with hydrophobic cores in brine in response to thermal input in situ generated well-dispersed hydrophilic nanogels, which showed a pronounced delayed swelling of a week compared to traditional nanogels showing swelling kinetics within minutes. Furthermore, the formation of swelling-delayed nanogels could occur at ambient temperature. This behavior was radically different from that of temperature-controlled labile cross-linkers containing nanogels, requiring temperatures greater than 50 °C for volume increase thanks to ester hydrolysis. In addition, the in-situ formed nanogels displayed long-term thermal stability and salinity tolerance under hostile media at temperatures up to 130 °C. The release of an acidic proton under aqueous conditions has been demonstrated to control the microenvironment for various scenarios. The nanotechnology of converting hydrophobic nanoparticles to hydrophilic nanogels could be applied in a wide range of practical applications such as plugging materials and foaming stabilizers for in-depth conformance control during water and CO2 flooding.
Keywords: environmentally responsive; hydrophilic nanogels; hydrophobic nanoparticles; oil recovery; thermal integrity.