Copolymer intercalated hydrotalcite sustained release-type fluid loss additive for water-based drilling fluid: Synthesis, characterization, and performance evaluation

The polyanionic copolymer fluid loss additive (PSADM) intercalated hydrotalcite sustained release-type fluid loss additive (PSADM–LDH) was fabricated through in situ intercalation polymerization to alleviate the deterioration of filtration and rheological properties of water-based drilling fluid (WBDF) under extreme geological conditions (e.g., high-temperature and alt-gypsum formations). The PSADM between layers of LDH can be slowly exchanged by anions in WBDF to give full play to its original efficiency. Results of FT–IR, TG and XRD demonstrate that the PSADM successfully intercalated the layers of LDH, and the intercalation rate was approximately 14 wt%. In addition, results of filtration measurements of WBDF demonstrate that the PSADM–LDH significantly decreased the filtration volume, even though after thermal rolling at 200 °C the filtration volume of brine drilling fluids contained 2 wt% PSADM–LDH was reduced by approximately 50% compared with PSADM. Moreover, the introduction of PSADM–LDH enhanced the thixotropy of WBDF because of forming a dynamic reversible gel structure by copolymer and charged clay colloidal particles (LDH and bentonite), which is conducive to giving full play to the water power of the bit, and carrying and suspending the drill cutting well in the annulus. Therefore, PSADM–LDH has broad application prospects for exploring and developing super-deep reservoirs.