Comb polymer/layered double hydroxide (LDH) composite as an ultrahigh temperature filtration reducer for water-based drilling fluids

In deep-formation drilling, effective filter loss control in ultrahigh-temperature conditions and high-salt conditions faces challenges. Comb polymer/LDH composites (P-LDH) with partially intercalated and partially exfoliated structures were prepared by in-situ polymerization as fluid loss materials. A series of characterization results showed that the P-LDH composites were successfully synthesized. P-LDH had partially intercalated and partially exfoliated structures and excellent thermal stability. In addition, the rheological evaluation results showed that P-LDH had a low viscosity effect while maintaining the rheological properties of the drilling fluid. P-LDH can significantly reduce the filtrate loss of drilling fluids at ultrahigh temperatures and high salt concentrations. At 240 °C and 15 wt% NaCl, the filtration loss was only 6.3 mL, and the high-temperature and high-pressure filtration loss was only 29.6 mL. Through the analysis of drilling fluid particle size and filter cake microstructure, based on hydrogen, ionic bonds, and intercalation effects, P-LDH acted closely with bentonite to promote stable dispersion, improve the drilling fluid’s stability, and form a dense filter cake to reduce the filtration loss. Therefore, P-LDH has broad application prospects in ultrahigh-temperature and high-salinity formation drilling.