Rheological and displacement performance of modified nano-SiO2 grafted polymeric system for enhanced oil recovery

Abstract

Polymer flooding is a widely used enhanced oil recovery technique, yet its efficiency is frequently limited by viscosity loss, shear degradation, and poor salt tolerance under harsh reservoir conditions. to address these challenges, this study presents a novel hybrid polymer nanocomposite, synthesized by grafting KH570-modified nano-SiO₂ into a poly(acrylamide-co-acrylic acid-co-2-acrylamido-2-methylpropanesulfonic acid) backbone. This molecular architecture has not been previously reported in EOR applications and provides dual advantages, such as robust covalent bonding between polymer and nanoparticle, and significantly enhanced nanoparticle dispersion within the polymer matrix. Comprehensive characterization using FTIR, SEM, and rheological analyses confirmed successful grafting and improved structural integrity. Unlike conventional polymer solutions, the new nanocomposite exhibited a 23 % higher viscosity retention in 10 g/L NaCl solutions, demonstrating excellent salt resistance and shear stability. Dynamic oscillation tests revealed significantly improved viscoelastic properties, suggesting superior performance in controlling mobility and minimizing viscous fingering. Core flooding experiments achieved an impressive oil recovery increase of 41–46 %, surpassing typical polymer flooding systems and highlighting the material's potential for improved sweep efficiency and conformance control in high salinity reservoirs. These results represent a significant breakthrough in polymer EOR technology, demonstrating that KH570-modified nano-SiO₂ grafting can effectively overcome traditional polymer limitations and offers promising pathway toward next generation EOR agents capable of maintaining performance under challenging reservoir conditions.