Synthesis, characterization and properties of an anionic polymer for water-based drilling fluid as an anti-high temperature and anti-salt contamination fluid loss control additive

An anionic polymer P (ANAN) of acrylamide, N -vinyl-2-pyrrolidone and 2-acrylamide-2-methylpropanesulfonic acid was synthesized through free radical polymerization and initiated by 2,2′-Azobis (2-methylpropionamide) dihydrochloride as an anti-high temperature and anti-calcium and magnesium contamination fluid loss control additive for water-based drilling fluid. The P (ANAN) was characterized by 13 C-NMR and 1 H-NMR, FTIR, elemental analysis and GPC analysis. The fluid loss tests were carried on different WBDFs. The results showed that this polymer can resist 4.5 × 10 5  ppm of Cl −1 , 4 × 10 5  ppm of Ca 2+ contamination at low pH environment caused by acid gas invasion in drilling fluid at 180 °C. The fluid loss control mechanisms of P (ANAN) were investigated by Zeta potential analysis, particle size distribution analysis and mud cake quality analysis. The thermal stability was investigated by TGA analysis. The results illustrate that the P (ANAN) exhibits a stronger interaction with clays and higher-temperature resistance, and it can improve the colloidal dispersion property obviously for drilling fluid under salts, calcium and magnesium contamination and even under circumstances of acid gas invasion conditions. Due to its superior fluid loss control properties, the P (ANAN) can be a promising polymer for water-based drilling fluid in deep and ultra-deep well drilling applications.