Water-soluble carboxymethylchitosan as green scale inhibitor in oil wells.

•Carboxymethylchitosan (CMC) was prepared and characterized by UV–vis, FT-IR and NMR.•The synthesis conditions led to a DS of 0.45 and water-solubility in all pH range.•CMC performance as a scale inhibitor was evaluated under physicochemical conditions of oil wells.•CMC acted as an environment friend scale inhibitor of CaCO3 under synthetic brine, at 1000 psi and 70 °C.•SEM images showed that CaCO3 crystals were deformed by CMC.