Nano-SiO2/Enzyme Composites and Their Effects on Viscosity and Degradation Kinetics of Oilfield Polymer

During well construction and reservoir development, polymer adsorption, plugging and retention in heterogeneous reservoirs can seriously hinder fluid injection and oil and gas production. In this study, we used α-amylase as a typical enzyme and designed a novel nano-SiO 2 /enzyme composite to achieve controlled degradation of targeted polymers in reservoirs. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and N 2 adsorption-desorption analysis confirmed successful encapsulation of α-amylase within nano-SiO 2 aggregates, albeit at the expense of the material specific surface area and pore volume. Performance evaluation revealed that the composites demonstrated exceptional specificity in degrading three common starch-based polymers (carboxymethyl starch, hydroxypropyl starch, and crosslinking starch) used in oilfields, achieving degradation efficiencies ( D e ) consistently above 95 %. Degradation kinetics analysis further demonstrated that increasing nano-SiO 2 content and pH led to a decrease in the reaction rate constant ( k , min -1 ) and a corresponding extension of the enzyme delayed-release time (half-life, t 1/2 ), whereas higher temperatures induced the opposite effect. Our results provide new insights into controllable enzyme degradation under reservoir conditions and provide a platform strategy for future development of enzyme degradation, including those effective toward acrylamide-based polymers.