Preparation and performances of a cationic modified polyacrylamide viscosity enhancer for water‐based drilling fluids.

Polyacrylamide and its derivatives are commonly used as viscosity enhancers in water‐based drilling fluids, but they have limitations in terms of salt resistance and temperature resistance. In this study, a novel cationic functional monomer, 4‐allylaminocarbonyl‐1‐dodecylpyridinium bromide, was introduced into the molecular chains of an acrylamide and acrylic acid copolymer in order to improve its temperature resistance and salt tolerance. Results showed that the apparent viscosity of a 2000 mg/L copolymer solution was 440.4 mPa s at a shear rate of 7.34 s−1, decreasing to 23.5 mPa s at 510 s−1 before recovering to 49.2 mPa s when the shear rate returned to 170 s−1. After 16 h of aging at 120°C, a brine drilling fluid containing 1% of the copolymer showed an apparent viscosity retention rate of 70%, likely due to the formation of a stable net structure between the copolymer's molecular chains and clay particles. These results suggest that the copolymer could be an excellent candidate for use as a viscosity enhancer in drilling fluids. [ABSTRACT FROM AUTHOR]