Green and Controllable Crosslinked Gel Plugging Technology Based on Modified Natural Biofibers

To overcome the limited mechanical strength and poor stability of conventional gels in high-temperature, high-salinity oilfield environments, a novel nanocellulose-reinforced hydrogel (AM/AA/PCNF) was developed through a multistep chemical modification strategy. Nanocellulose served as a rigid backbone and was successively modified via epoxide ring-opening, methacryloyl esterification, and polydopamine functionalization, forming a three-dimensional network with multiple dynamic crosslinking interactions. The resulting composite hydrogel exhibited outstanding comprehensive properties when the PCNF content was 3 wt%: a tensile strength of 2.6 MPa, fracture energy of 8.95 MJ/m3, and compressive strength of 360 kPa—all markedly superior to those of conventional hydrogel systems. Under simulated downhole conditions (120 °C, 6 MPa, and 5 wt% salinity), the hydrogel demonstrated excellent plugging performance across sand beds of varying particle sizes (60–80 mesh to 20–40 mesh), maintaining cumulative fluid loss within 28.4–42.5 mL. Mechanistic investigations indicate that the enhanced performance stems from the synergistic combination of a rigid nanocellulose scaffold and multiple dynamic interactions, which facilitate a self-adaptive plugging mechanism. The study delivers both theoretical and practical foundations for designing advanced plugging systems.