Development and performance evaluation of vinyl-modified silica nanoparticles to enhance polymer-based filtration control in high-temperature water-based drilling fluids

To address the failure of traditional filtration reducers under high-temperature and high-salinity conditions in ultra-deep drilling, this study developed a novel organic–inorganic hybrid nanocomposite filtrate reducer (Nano-DAND). Nano-DAND was synthesized via free-radical copolymerization of N,N-diethylacrylamide (DEAM), 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), acryloyloxyethyltrimethyl ammonium chloride (DAC), and N-vinylcaprolactam (NVCl), reinforced with vinyl-functionalized silica nanoparticles (SVS) prepared by SDS-assisted dispersion and vinyltriethoxysilane (VTES) surface modification. Structural characterization (FTIR, ¹H NMR, TGA, TEM, and PSD) confirmed the successful incorporation of SVS into the polymer matrix, with Nano-DAND exhibiting high thermal stability (decomposition temperature > 331 °C). Under 240 °C and 20 wt% NaCl, Nano-DAND achieved FL API of 7.8 mL and FL HTHP fluid loss of 31.2 mL, significantly outperforming commercial additives such as Driscal-D and Polydrill, exhibiting FL HTHP at 81.8 mL and 114.8 mL, respectively. SEM analysis of filter cakes showed that Nano-DAND formed a dense and uniform mud cake, effectively reducing porosity and permeability. Rheological tests indicated that Nano-DAND maintained good viscosity retention (>50 %) after thermal aging, Adsorption and zeta potential analyses revealed that Nano-DAND interacts with bentonite platelets through hydrogen bonding, electrostatic attraction, and ionic bridging, forming a stable three-dimensional network that enhances filter cake integrity and suppresses fluid loss. These findings highlight Nano-DAND’s potential as a robust filtration control agent for ultra-deep drilling applications.