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Abstract: Shale gas development often suffers from wellbore instability due to microfractures in the formation, posing serious challenges to drilling safety and efficiency. This study presents a functionalized graphene oxide (GO-PAA) nanomaterial, prepared by grafting hydrophilic polyacrylic acid (PAA) chains onto GO surfaces to enhance dispersion stability under high salinity, elevated temperature, and wide pH conditions. The results indicate that GO-PAA effectively resists charge-shielding effects under conditions of high salinity, elevated temperature, and a wide pH range, significantly reducing the risk of particle aggregation. Even at high salt concentrations, the zeta potential remains below ?32.8 mV, demonstrating good colloidal stability. Plugging performance was evaluated using simulated core experiments. GO-PAA formed a “band-aid” like barrier on shale microfracture surfaces, reducing permeability by up to 57.53%, nearly twice that of conventional spherical nanoparticles. Scanning electron microscope (SEM) and elemental analysis confirmed the formation of a dense and uniform plugging layer. The synergistic interaction between GO’s 2D lamellar structure and the flexible polymer chains facilitated effective surface adhesion and coverage. This adsorption–adhesion plugging mechanism represents a shift from traditional bridging theories, enabling reduced material usage and improved efficiency. The findings provide theoretical and practical support for designing high-performance nanoplugging agents in water-based drilling fluids, contributing to safer and more sustainable shale gas development.