Experiment-supported simulation of silica nanofluid alternating CO2 injection: Sensitivity analysis for enhanced oil recovery and CO2 storage in sandstone reservoirs

Water-based nanofluid alternating gas (NWAG) injection is a promising approach for enhancing oil recovery in carbonate and sandstone reservoirs. The NWAG injection performance is influenced by multiple parameters, which necessitates sensitivity analysis using computer simulation. NWAG simulations have been reported for carbonate reservoirs. However, in sandstone, the NWAG method has only been studied through laboratory experiments. This study aims to investigate the reliability of the NWAG method in sandstone on a large scale by making a simulation and performing sensitivity analysis for the slug size, NWAG ratio, and nanoparticle concentration in a three-dimensional model of a sandstone reservoir. Silica nanofluid and CO 2 were chosen to investigate oil recovery and CO 2 storage performance during NWAG injection. A reservoir-scale model was constructed by upscaling a laboratory-validated one-dimensional model based on a core flooding experiment. Subsequently, several simulations were performed to determine the effects of each parameter. Results indicated that a slug size of 0.2 hydrocarbon pore volume, NWAG ratio of 1:1, and nanoparticle concentration of 0.5 wt% resulted in the fastest oil recovery. Moreover, results suggested that nanofluid plays two equally important roles, controlling gas mobility and altering rock wettability, and focusing only on one aspect leads to inferior results. For CO 2 storage, larger slug sizes and higher gas ratios resulted in greater CO 2 storage but at the expense of longer operation time for the same amount of oil produced. Overall, the study findings demonstrate that by using the right parameters, NWAG injection can be effective for simultaneous oil recovery and CO 2 storage in sandstone reservoirs. • 3D sandstone reservoir simulation of nanoparticle–CO 2 alternating injection. • Nanoparticle adsorption on sandstone was lab-measured and added to the model. • Sensitivity analysis showed effects of slug size, injection ratio, and concentration. • Smaller slug sizes and balanced injection ratios enhanced oil recovery efficiency. • Larger slugs and higher gas ratios significantly improved CO 2 storage capacity.