Laboratory and Simulation Studies of Novel Hybrid Nano-Polymer EOR in Carbonate Reservoirs

Abstract Innovative enhanced oil recovery (EOR) strategies are needed to unlock additional reserves in heterogeneous, oil-wet carbonate reservoirs. This study evaluates hybrid nano-polymer flooding by integrating silica nanoparticles (SiO₂) and single-walled carbon nanotubes (CNT) with hydrolysed polyacrylamide (HPAM) to optimize wettability alteration, injection parameters, and recovery mechanisms. A combined experimental and numerical approach was employed, where rheological tests assessed viscosity enhancement under varying shear conditions, and wettability alteration was quantified via contact angle measurements using both HPAM-SiO₂ and HPAM-CNT systems. Core floods were performed in three consecutive phases; waterflooding (baseline), standalone nanoparticle flooding, and followed by hybrid nano-polymer flooding to systematically assess the performance of each method. Key parameters monitored included oil recovery, pressure differentials, injectivity reduction, resistance factor, and residual resistance factor. The experimental data were history matched to validate a numerical model that exactly replicated the laboratory results, providing a strong foundation for future EOR studies. Rheological evaluations confirmed that the hybrid formulations maintained a stable target viscosity (4 cP) under reservoir conditions, ensuring effective mobility control without compromising polymer functionality. Wettability studies demonstrated significant shifts; the HPAM-SiO₂ system reduced contact angles from 168° to 54.9°, while the HPAM- CNT system shifted from 171° to 38.66°, thereby enhancing fluid displacement efficiency. Core flooding experiments revealed that standalone SiO₂ and CNT flooding improved recovery by 2% and 7%, respectively, whereas the hybrid systems achieved incremental gains of 6% and 18%, driven by the combined effects of wettability alteration and viscosity stability. Injectivity metrics showed favourable resistance factors and sustained residual resistance factors, outperforming polymer only methods. This study presents the first core scale evaluation of novel hybrid nano-polymer flooding in carbonate reservoirs, combining experimental outcomes with a validated numerical model to provide guidelines for field implementation and risk assessment, suggesting significant scalability for Gulf region applications.