Preparation of a novel amphiphilic comb-like terpolymer as viscosifying additive in low-solid drilling fluid

•A novel amphiphilic comb-like terpolymer PASA was synthesized.•Its rheology, filtration loss and Zeta potentials in drilling fluids were evaluated.•The salt- and thermal-resistance properties of drilling fluids were improved by PASA.•The reason is its comb-like structure, electrostatic stability and network structure.

Comb-like polymers have attracted a strong research interest due to their many attractive properties. Novel amphiphilic comb-like terpolymer (PASA), as viscosifying additive for low-solid drilling fluid under high temperature and salinity, was prepared and characterized by FTIR, 1H-NMR and TGA. PASA possessed excellent thermal stability. The rheological properties, filtration properties and negative Zeta potentials of both freshwater drilling fluid and saturated salt-water drilling fluid were greatly improved by adding PASA before and after thermal aging tests, due to comb-like conformation of PASA, strong electrical double layer force of bentonite particles and stable network structure formed by PASA and bentonite particles.

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