Water-soluble carboxymethylchitosan as green scale inhibitor in oil wells

Abstract A water-soluble carboxymethylchitosan (CMC) was prepared in water/isopropanol (2/8) medium, at 10 °C, and characterized by UV–vis, FT-IR and NMR techniques. Its performance as an environmentally friendly scale inhibitor in oil wells was evaluated under the physicochemical conditions of oil wells in northeast of Brazil, by using SEM, visual compatibility and dynamic tube blocking test. The synthesis conditions led to a degree of carboxymethylation of 0.45 and water-solubility in all pH range studied (1–11). CMC acted as a scale inhibitor of CaCO 3 under synthetic brine medium, presenting a minimum inhibitor concentration (MIC) of 170 ppm (1000 psi, T = 70 °C). SEM images showed that CaCO 3 crystals were deformed by CMC, which was attributed to effective interactions of CMC through its carboxylate ions and lone pair of electrons on OH and NH 2 groups with calcium ions, preventing scale deposition.