On the effect of salinity and nano-particles on polymer flooding in a heterogeneous porous media: Experimental and modeling approaches

In this study, polymer flooding process was simulated using COMSOL Multiphysics (R) modeling software. Navier-Stokes and phase field equations were solved simultaneously using finite element approach. Effects of salinity, viscosity, and nano-particles were studied on displacement efficiency of oil sample in the heterogeneous porous media. Modeling results for oil recovery factor and breakthrough time were obtained and compared to experimental outputs of another study. Results indicated that there exists a proper accommodation between the results. Errors ranged from 3% to 7% for oil recovery factor and 0.5%-0.9% for the breakthrough time in various injection scenarios. Using predefined structure of the under test micromodel, star-like meshes were developed in this software for the first time. This unstructured mesh is more likely to the pore structures of the sandstone reservoirs. To increase the validity of the results, a boundary layer was designated in the fluid flow path and mesh generation was performed manually in a complicated pore space instead of automatic mesh generation. Experimental and modeling results for the residual oil saturation as a function of dimensionless time were compared. Mesh dependency studies were performed to obtain the best number of mesh elements in which the most accurate results were obtained in the minimum required time. Finally, sensitivity analysis studies were performed as a function of injection rate, mobility ratio, and viscosity and the operating conditions were analyzed in terms of capillary number. All the polymer injection scenarios led to reasonable range for this parameter which verifies the accuracy of the selected operating parameters and the modeling approach.