Development and Assessment of the Synergistic Inhibition Efficiency of IA/AMPS Copolymers for Inhibiting CaCO₃ and CaSO₄ Co-production in Oilfield Scale

Polycarboxylate-scale inhibitors (PSI) are widely utilised in managing oilfield mineral scales, not only due to their high complexation, increased dispersion, and high thermal stability, but also due to their environmental compatibility, as they are phosphorus-free. However, they are effective in inhibiting only one specific scale. Thus, new non-phosphorus multifunctional SI is in demand immediately, where the scale can be made up of a combination of two or more minerals. Itaconic acid/ 2-acrylamido-2-methylpropane sulfuric acid (IA/AMPS) novel copolymer is synthesised via a free radical polymerisation to inhibit the CaCO₃ and CaSO₄ scales. The functional groups believed to be effective in inhibiting the scales were characterised using FTIR. The IA/AMPS performance was investigated to determine the optimal synthesis parameters/ conditions for the dispersion property. Results show that the best conditions for IA/AMPS copolymer preparation included a 1:2 molar ratio of IA to AMPS, 7% of initiator dosage and monomer total mass, a 4:1 molar ratio of ammonium persulfate (APS) to sodium bisulfite, 90 °C of reaction temperature, and 7 hours of the reaction period. Based on the qualitative observations, the IA/AMPS scale inhibitor effectively reduces the formation and surface adherence of both CaCO₃ and CaSO₄ scales. It significantly lowers the scale density and promotes the formation of less adherent, finer particles, especially under elevated temperatures. The combined effect of IA/AMPS and heat demonstrates a synergistic inhibition, particularly evident in the complete prevention of CaSO₄ scale at 80 °C.