Preparation and Performance of High-Temperature-Resistant and Eco-Friendly Fluid Loss Reducer

This study addresses the current challenge of balancing high-temperature resistance and environmental performance in fluid loss reducers. Using grape extract (GE), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), acrylamide (AM), and sodium lignosulfonate (LS) as monomers, we successfully synthesized an environmentally friendly fluid loss reducer, GE/AMPS/AM/LS polycopolymer (GE-AAS), that can withstand temperatures of 200 °C through copolymerization and cross-linking reactions. The successful synthesis of GE-AAS was validated using Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR) spectroscopy, and scanning electron microscopy (SEM), which also highlighted its linear molecular structure characteristics. Thermogravimetric analysis (TG) results indicate that thermal decomposition begins at 290 °C and demonstrate excellent thermal stability. The filtration loss experiment showed that after 16 h of aging at 200 °C, the medium-pressure fluid loss (API) and high-temperature, high-pressure filtration loss (HTHP) of the base mud containing 3% GE-AAS were 8.8 and 34.2 mL, respectively, demonstrating excellent filtration loss reduction performance. The mechanism of action of GE-AAS was revealed through analyses such as particle size distribution, zeta potential, atomic force microscopy (AFM), and scanning electron microscopy (SEM). It was strongly adsorbed onto the bentonite surface primarily via hydrogen bonds, ionic bonds, and electrostatic interactions, which increased the electrostatic repulsion among bentonite particles, facilitated their dispersion, and led to the formation of a thin, dense mud cake. In addition, GE-AAS showed a half-maximal effective concentration (EC50) of 5.6 × 105 mg/L and a biochemical oxygen demand (BOD5)/chemical oxygen demand (CODCr) ratio of 33.6%, indicating that it is nontoxic and biodegradable.