Mechanism of oil displacement during polymer flooding in porous media with micro-inhomogeneities

Enhanced oil recovery (EOR) process selection is an important part of field development strategy. One of the most important categories of EOR methods utilize certain chemical components that enhance the fluid properties. Polymer-enhanced waterfloods are one of the examples. During conventional waterfloods, the flow characteristics and displacement efficiency usually depends on a certain rock type in study. In a chemical EOR flood, there are a large number of parameters needed to be defined and optimized that impact process efficiency. The attempt to execute corefloods for various combinations of these parameters for each rock type would lead to a large number of tests not executable in a time frame compatible with timely decision making. And the destructive nature of the experimental chemical EOR floods prohibits repeated testing on the same core sample. The natural difference between the samples selected for the study can prevail over the process efficiency difference related to the certain design parameter in the study. Digital core analysis can help to optimize design of EOR floods and reduce the associated uncertainty. In this work we apply digital core analysis to investigate the dynamics of oil displacement, using water and water-based polymer solutions in porous media. The described technology application includes scanning of core samples using X-ray microtomography, creating digital models for the samples in study, and running pore-scale hydrodynamic modeling using the density functional hydrodynamics (DFH) method, which combines density functional theory with compositional multiphase hydrodynamics. The results include visual snapshots of phase distributions at pore scale for various times during the waterflooding and polymer solution flooding at various concentrations. Polymer-enhanced waterflooding increased the displacement coefficient by almost 2% and 20% for low- and high-concentrated polymer solutions, respectively. This effect was further explained by analyzing the dynamics of oil displacement on a pore scale. The results show an exemplary sensitivity study that investigates the dependency of the displacement coefficient on the polymer solution type and concentration. Additional sensitity studies with varying design parameters (slug size, injection sequence, polymer type, etc.) can be also performed.