Development of a novel magnetic nanocomposite crosslinker for enhanced polymer gelation applications

High-temperature degradation and excessive syneresis severely limit the lifespan of polymer gels used for water shutoff in mature reservoirs. This study investigates the synthesis and application of a novel Fe 3 O 4 @saponin/Cu(II) nanocomposite as a multifunctional reinforcement for Hydrolyzed Polyacrylamide (HPAM)/Cr(III) systems, specifically designed to overcome stability failures in harsh environments. Magnetite cores were surface-functionalized with saponin and copper(II) ions to create a dual-mechanism crosslinker, which was subsequently characterized via FTIR, TGA, and DLS. The performance of the resulting nanocomposite gels was evaluated through rheological profiling, long-term thermal aging at 105 °C, and high-pressure core flooding experiments in sandstone plugs. Results indicate that an optimal loading of 500 ppm increased the gel’s storage modulus by threefold compared to the nano-free control and accelerated gelation time to a field-practical 10 h. Critically, the nanocomposite effectively arrested network collapse, reducing syneresis from 72.8% to only 10% after two months. Furthermore, core flooding tests revealed a dramatic enhancement in sealing capacity, with Residual Resistance Factors (RRF) exceeding 1000, more than 30 times higher than that of the conventional system. These findings demonstrate that the synergistic combination of steric stabilization by saponin and secondary coordination bonding by Cu(II) creates a highly durable network, positioning this nanocomposite as a promising candidate for sustainable conformance control in high-temperature, high-salinity reservoirs.