Synergistic reinforcement of HPAM/Cr(III) acetate polymer gels using Fe₃O₄@Saponin/Ni nanocomposites for conformance control applications

The persistent challenge of gel instability and inadequate performance under harsh reservoir conditions limits the efficiency of polymer-based systems in enhanced oil recovery (EOR) and water shutoff operations. This study addresses these limitations by introducing Fe₃O₄@Saponin/Ni nanocomposites as synergistic reinforcing agents within a standard HPAM/Cr(III) acetate gel system. Distinct from earlier nanocomposite additives, the specific incorporation of Nickel ions into the saponin-functionalized magnetite lattice provides a novel advantage: the formation of thermally durable Ni-O-Fe bonds and additional coordination sites that significantly enhance the gel's resistance to thermal degradation and syneresis. Fe₃O₄ nanoparticles were synthesized and sequentially functionalized to ensure optimal dispersion and secondary crosslinking efficiency. Comprehensive characterization was performed using FT-IR, TGA, SEM, and DLS, followed by evaluation of gelation kinetics, dispersion stability, rheology, syneresis resistance, and core flooding performance under reservoir-mimicking conditions. Results revealed that the unique Ni-doped structure improved thermal stability, ensured uniform nanoparticle size (20-50 nm), and promoted stable dispersion up to 500 ppm. The addition of these nanocomposites accelerated gelation rates at optimal concentrations (≤ 250 ppm), enhanced storage modulus, and dramatically reduced syneresis, exhibiting only 12% weight loss after two months at 110 °C and 3000 psi. Core flooding tests confirmed the superior plugging efficiency, higher resistance factors, and long-term durability of the nanocomposite-reinforced gels compared to conventional formulations. These findings demonstrate that Fe₃O₄@Saponin/Ni nanocomposites provide a robust, multifunctional platform for advanced EOR, offering sustained mechanical and thermal resilience in demanding environments.