<i>In Situ</i> Generated Hydrogels Exhibiting Simultaneous High-Temperature and High-Salinity Resistance for Deep Hydrocarbon Reservoir Exploitation

Hydrogels are extensively utilized in the upstream of the oil and gas industry, serving as plugging agents, fracturing fluids, and profile control materials. However, their limited resistance to high temperatures and high salinities poses a significant challenge that impedes their applications in deep reservoirs. Herein, 2-acrylamido-2-methylpropanesulfonic acid (AMPS) functionalized polyacrylamides P(AM-co-AMPS) with varying AMPS content from 0 to 75 mol % were designed, which were cross-linked with phenol formaldehyde resin in brine solutions containing 20% NaCl + 0–3.0% CaCl2. The relationship among salinity, AMPS molar content, and hydrogel performance has been systematically analyzed and discussed. The Ca2+ in brine could form supramolecular interaction with the carboxylate groups generated by hydrolysis, thereby forming a dual cross-linked network hydrogel. The dual cross-linked network of the hydrogel exhibits exceptional performance up to 160 °C in brine containing 20% NaCl and 3.0% CaCl2. This advancement could serve as an alternative solution for deep oil and gas reservoirs and provide valuable insights for designing novel polymer hydrogels with outstanding features such as high-temperature and high-salinity resistance, as well as delayed cross-linking capability.