A sustainable approach to synthesize phosphonated chitosan using ball milling and its application for oilfield scale management

For many years, the oil and gas industry has strived to develop environmentally friendly organophosphorus-based scale inhibitors. The natural polymer chitosan has recently gained significant importance for various upstream oil and gas applications. We earlier reported the synthesis of phosphonated chitosan (PCH) under conventional conditions in a two-step pathway via the Kabachnik-Fields reaction. This earlier work showed that PCH displayed good performance against calcite scaling and weak efficiency for barite scaling using a high-pressure dynamic tube-blocking rig at 80 bar and 100 °C using a produced water composition from the Heidrun oilfield, Norway. The mechanochemical synthesis approach has recently emerged as a powerful, green, and sustainable protocol in several industrial and academic applications. Herein, we report for the first time the synthesis of PCHvia the Moedritzer-Irani reaction using the ball-milling technique under liquid-assisted grinding conditions. The static inhibition performance of PCH is investigated, for the first time, against the gypsum scale and the calcite scale based on the NACE Standard TM0374-2007 protocol. The results are compared to the commercial polysaccharide, carboxymethyl inulin, (CMI), and aminotrismethylenephosphonic acid (ATMP) scale inhibitors. Furthermore, PCH was screened against the Heidrun calcite scale using static jar tests. The thermal stability and calcium compatibility properties of the mechanochemically synthesized PCH were investigated. The polymer exhibited an outstanding inhibition efficiency against both oilfield scales. It was also found that PCH showed excellent thermal stability after 7 days at 130 °C and excellent calcium compatibility properties at high calcium ion concentrations. Density functional theory (DFT) simulations were carried out to gain atomic insight into the interaction of PCH, CMI, and ATMP with the mineral surface.