Novel Acrylamide/2-Acrylamide-2-3 Methylpropanesulfonic Acid/Styrene/Maleic Anhydride Polymer-Based CaCO(3) Nanoparticles to Improve the Filtration of Water-Based Drilling Fluids at High Temperature

Filtration loss control under high-temperature conditions is a worldwide issue among water-based drilling fluids (WBDFs). A core–shell high-temperature filter reducer (PAASM-CaCO(3)) that combines organic macromolecules with inorganic nanomaterials was developed by combining acrylamide (AM), 2-acrylamide-2-methylpropane sulfonic acid (AMPS), styrene (St), and maleic anhydride (MA) as monomers and nano-calcium carbonate (NCC). The molecular structure of PAASM-CaCO(3) was characterized. The average molecular weight of the organic part was 6.98 × 10(5) and the thermal decomposition temperature was about 300 °C. PAASM-CaCO(3) had a better high-temperature resistance. The rheological properties and filtration performance of drilling fluids treated with PAASM-CaCO(3) were stable before and after aging at 200 °C/16 h, and the effect of filtration control was better than that of commonly used filter reducers. PAASM-CaCO(3) improved colloidal stability and mud cake quality at high temperatures.