Preparation and application of a novel high temperature resistant filtration reducer in water-based drilling fluids

4-vinylpyridine (VP), N, N-dimethylacrylamide (DMAA), 2-Acrylamido-2-methylpropane sulfonic acid (AMPS) and sodium styrene sulfonate (SSS) were synthesized to a novel filtrate reducer in aqueous solution by free radical copolymerization using ammonium persulfate and sodium bisulfite as redox systems. The structure of copolymer was characterized by Fourier transform infrared spectroscopy (FT-IR). Thermogravimetric analysis (TGA) showed that the thermal decomposition temperature of the copolymer was higher than 310°C, which indicated that the copolymer had excellent high temperature resistance. At the same time, the rheological and filtration properties of water-based drilling fluids (WBDFs) were further evaluated by adding copolymer as a filtrate reducer. The results showed that the fluid loss (FLAPI) of WBDFs was only 5.0 mL when the copolymer content is 2.0 wt%, Even after hot rolling at 260°C for 16 hours, the FLAPI of WBDFs was 8.2 mL. The FLAPI of fresh water mud was 25.2 mL, and that of aged fresh water mud was 48 mL. In addition, WBDFs with copolymer effectively resists salt and calcium intrusion before and after hot rolling at high temperature for 16 hours, which indicates that the copolymer can be used as an efficient filtration reducer in ultra-deep well drilling operations.