Poly(ionic liquids) based on β-cyclodextrin as fluid loss additive in water-based drilling fluids

•Poly(ionic liquids) (PILs) based on β-cyclodextrin were satisfactorily synthesized.•The thermal degradation of PILs occurred after 300 °C and had excellent thermal stability.•PILs were initially implemented as fluid loss additive in water-based drilling fluids.•PILs demonstrated efficient fluid loss control in extreme harsh environments at 180 °C.•PILs facilitates the establishment of mud cake with low permeability and thin. Well wall collapse due to massive fluid in water-based drilling fluids (WDFs) intrusion into the reservoir is an urgent issue during oil drilling. In this study, we synthesized the poly(ionic liquids) (PILs) based on β-cyclodextrin and investigated its novel application as fluid loss additive in WDFs. American Petroleum Institute standard filtration tests showed that the PILs exhibited excellent filtration control performance even after hot rolling at 180 °C for 16 h compared to commercial fluid loss additives (Driscal D, PAC-Lv, CMC). Specifically, the fluid loss volumes of Driscal D/WDFs, PAC-Lv/WDFs and CMC/WDFs were 10.4 mL, 12.4 mL and 14.8 mL respectively after hot roll at 180 °C for 16 h, however, the fluid loss of PILs/WDFs was only 2.8 mL. The extremely low filtration rate, thickness and permeability of the PILs/WDFs mud cake resulted in exceptionally low fluid loss volume. Additionally, the mechanism of PILs controlling fluid loss in WDFs was revealed by bentonite particle size measurement and Zeta potential measurement. This work demonstrates that PILs have the promising application as an efficient fluid loss additive in WDFs due to the outstanding filtration loss reduction behavior.