Sustainable Self-Healing Thermoresponsive Nanocomposite Derived from Shrimp Shells and Lignin Biowaste for Water Shutoff in Ultradeep High-Temperature, High-Salinity Carbonate Reservoirs

Abstract Excessive water production in ultradeep, extreme high-temperature and high-salinity (HTHS) carbonate reservoirs has emerged as a major challenge, reducing hydrocarbon productivity and creating substantial environmental and economic burdens. Herein, we report, for the first time, the synthesis of a novel, highly resilient, sustainable, self-healing, thermoresponsive chitin-based nanocomposite hydrogel for water shutoff, specifically tailored to endure extreme harsh conditions of 160 °C and 350,000 ppm salinity. The nanocomposite was synthesized via a near-zero-waste approach utilizing chitin and CaCO3 nanoparticles derived from shrimp shell biomass, employing a recyclable, CO2-switchable natural deep eutectic solvent (NADES)-assisted enzymatic process. The extracted chitin was copolymerized with vinyl ester sulfonated lignin (VESL), a green macromonomer derived from industrial lignin waste, and 1-vinylimidazole (VIm) via free radical polymerization. The hydrogel composition has been optimized using response surface methodology (RSM) with central composite design. The nanocomposite was thoroughly characterized by FTIR, 1H NMR, SEM, EDX, TGA, and DTG analysis. The optimized nanocomposite demonstrated a superior swelling ratio and viscoelastic properties even at an ultralow polymer concentration of 0.08 wt % across temperatures of 25 to 160 °C and salinities up to 350,000 ppm. Core-flooding experiments indicated effective fracture plugging with high RRF values of 300.5 ± 5.7 and 191.1 ± 4.8 (with plugging efficiencies of 99.7 ± 0.4% and 99.5 ± 0.5%, respectively) using ultralow nanocomposite concentrations of 0.08 wt % and 0.1 wt %, respectively. This research presents a sustainable strategy that integrates the CO2-switchable green extraction of chitin with lignin for valorization of marine and industrial biowaste into a high-performance self-healing hydrogel for water shutoff in ultra-HTHS reservoirs.