High‐Performance Core–Shell Structural Blocking Agents of P( <scp>DMDAAC</scp> / <scp>AMPS</scp> / <scp>ACMO</scp> )@ <scp>TiO</scp> ₂ for Water‐Based Drilling Fluid

ABSTRACT In this study, a core–shell structured nanoblocking agent (TDAA) was synthesized via aqueous‐phase polymerization, employing KH570‐modified TiO 2 as the inorganic core and a copolymer shell composed of DMDAAC, AMPS, and ACMO. Structural and compositional characterizations confirmed the successful formation of a uniform core–shell morphology with favorable aqueous dispersibility and thermal stability. Performance evaluation demonstrated that the incorporation of TDAA into water‐based drilling fluid (WBDF) effectively improved its high‐temperature rheological and filtration properties. At an optimal concentration of 2.5 wt%, after 180°C hot rolling for 16 h, the apparent viscosity (AV), plastic viscosity (PV), and yield point (YP) increased from 4 to 13.5 mPa s, 3 to 11.5 mPa s, and 1 to 2 Pa, respectively. Concurrently, the filtration loss at ambient conditions (FL API ) decreased from 56.0 to 6.4 mL, while the high‐temperature, high‐pressure filtration loss (FL HTHP ) declined from 117.0 to 16.4 mL. Plugging performance tests using membranes with varying pore sizes indicated that TDAA exhibited optimal sealing capability at a pore size of 200 nm, with cumulative filtration loss controlled at 14.4 mL. Morphological and interfacial analyses confirmed that the core–shell architecture facilitated the formation of compact filter cakes. These findings highlight the potential of TDAA for use as a high‐performance sealing agent in high‐temperature, high‐pressure drilling environments.