Study on the Scale Inhibition Performance and Mechanism of a High-Performance Graft Copolymer Cellulose Green Scale Inhibitor on Oilfield Ca²⁺

Carboxymethyl cellulose (CMC), acrylic acid (AA), acrylamide (AM), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) were subjected to graft copolymerization through a free radical polymerization process, yielding four distinct CMC-g-P(AA-co-AM-co-AMPS) scale inhibitors. The assessment revealed that the scale inhibitors significantly mitigated the formation of the CaCO3 scale, with an inhibition efficiency ranging from 98% to 100%, surpassing that of unmodified CMC by a factor of more than three. The mechanism of scale inhibition was confirmed utilizing static scale inhibition experiments, scanning electron microscopy (SEM), X-ray diffraction (XRD), zeta potential, and molecular dynamic simulation. Additionally, the impact of the grafting ratio and graft chain distribution on the inhibition efficiency was scrutinized. It was established that, among samples with comparable grafting ratios, those with a higher average number of graft chains exhibited a greater number of active inhibition sites, leading to enhanced scale inhibition efficacy. The presence of inhibitors induces dispersion and chelation, which in turn cause lattice distortions in CaCO3 crystal nuclei, thereby kinetically stabilizing the vaterite and aragonite polymorphs. This research presents a methodology for developing scale inhibitors suitable for oil field applications and furnishes theoretical underpinnings for the fabrication of efficient and eco-friendly scale inhibitors.