Polymer–SiO₂/Laponite Composite as a Filtrate Reducer for High-Temperature and High-Salt Drilling Fluids

Water-based drilling fluids are prone to contamination by high temperatures and high salt, resulting in a deteriorated filtration performance of the drilling fluids, posing a significant threat to the safety of drilling operations. This study utilized N, N -dimethylacrylamide (DMAA), 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), dimethyldiallylammonium chloride (DMDAAC), N -vinylpyrrolidone (NVP), and nanomaterials (nano-SiO 2 and nanolaponite) to prepare a polymer nanocomposite NP-3 as a filtratef reducer for drilling fluids. The thermal stability evaluation of the polymer solution revealed that the thermal degradation temperature order of the different structural units of the polymer is DMAA < AMPS ≈ DMDAAC < NVP, and the temperature resistance of NP-3 in the solution is 220 °C. Evaluation of drilling fluid performance demonstrated that 3.5 wt % NP-3 enabled the drilling fluid to resist contamination from 15 wt % NaCl at 230 °C, with an American Petroleum Institute (API) filtration loss and high-temperature and high-pressure (HTHP) filtration loss after hot rolling of 4.2 and 22.0 mL, respectively. At high temperatures, the degradation of the polymer composite releases nanoparticles, which enhance the density of the filter cake, allowing for adjustable and enhanced control of filtration performance of drilling fluids under high-temperature and high-salty conditions.