Preparation of Green Sustained-Release Solid Scale Inhibitor for Inhibiting CaSO4 Scale in Oilfield Applications

Abstract

Severe calcium sulfate (CaSO4) scaling and the inability to monitor inhibitor concentrations in real time remain critical challenges in oilfield waterflooding operations. To address these, a novel fluorescent-responsive polymeric inhibitor, P(MA-SSS)-g-Cur, was synthesized and subsequently encapsulated within a cross-linked poly(vinyl alcohol) matrix to develop a green, sustained-release solid inhibitor (CP(MA-SSS)-g-Cur). The synthesized P(MA-SSS)-g-Cur exhibited a strong linear fluorescence response (R2 = 0.9970) within the concentration range of 2–12 mg·L–1, enabling highly sensitive online monitoring. Under optimal static conditions (inhibitor dosage of 40 mg·L–1, total dissolved solids of 35 g·L–1, pH = 7, and T = 70 °C), it demonstrated an excellent inhibition efficiency of 99.5% against CaSO4. Furthermore, the solid formulation displayed a robust 60-day sustained-release profile, successfully maintaining a high CaSO4 inhibition efficiency of 99.8%. Microscopic and mechanistic analyses revealed that this superior antiscaling performance is attributed to the synergistic effects of cation chelation, electrostatic repulsion, steric hindrance, and induced lattice distortion. This work provides a highly effective, traceable, and long-acting strategy for mitigating severe scale deposition in dynamic oilfield environments.