Laboratory Investigation of Hybrid Nano-Assisted-Polymer Method for EOR Applications in Carbonate Reservoirs

Currently, there has been a surge in evaluating the effectiveness of various hybrid enhanced oil recovery (EOR) methods as they combine the benefits of standalone processes. This study focuses on laboratory investigation to evaluate synergy between polymer and nanoparticles (NP), as their combination can simultaneously alter capillary and viscous forces. N-vinyl-pyrrolidone-based partially hydrolyzed polyacrylamide and silica oxide nanoparticles are used in this study. The standalone polymer, nanofluid (NF), and combined polymer-nanofluid solutions are prepared in different salinities (1200-40,000 ppm). The zeta potential of solutions is measured to determine the stability of NF at various salinities. Contact angle measurements are performed to determine the optimum concentration of NP. A series of rheological experiments are accomplished at different nanoparticle concentrations (0.05, 0.1, 0.15 wt%), temperatures (25-80 °C), and polymer concentrations (500 to 3000 ppm). Additionally, a long-term stability test was conducted over thirty days at 80°C on nano-assisted-polymer fluid over a long period. Zeta potential results proved that the stability of nanofluids decreases with an increase in solution salinity. However, the addition of polymer has a positive impact on the stability of NF and is stable up to 40 000 ppm salinity. The nanoparticles have shown potential in altering the wettability of the rock toward the intermediate wet conditions. A maximum deviation of 55° in contact angle is observed for a 0.1 wt% NP solution and is selected as optimum concentration. Rheology studies illustrate that the addition of NP increases the viscosity of the polymer solution by 25%. All nano-assisted-polymer solutions tested in this study showed shear thinning behavior. Long-term thermal stability of nano-assisted-polymer solution indicates that the solution achieves equilibrium after 5 days and maintains target viscosity of 4 cP. The addition of polymer has positively impacted the salinity tolerance of nanoparticles. Additionally, nanoparticles improved the viscosity of the polymer solution. This study will open new doors for the hybrid EOR method.