Numerical Simulation of Polymer Flooding Including the Effects of Salinity
Oil recovery by polymer flooding is influenced by reservoir heterogeneity not only through its effects on crossflow, but also through the dependence on polymer adsorption, polymer viscosity, and permeability reduction on the system properties. A simulator is described that accounts for all of these factors. Non-Newtonian behavior, permeability reduction, polymer adsorption, dispersion of the polymer and electrolyte, and inaccessible pore volume are all modeled as a function of the polymer concentration, brine salinity, rock properties, and flow conditions. A standard two-phase and two-dimensional finite difference simulator was developed with the added feature of the moving point technique to solve concentration balances. This feature virtually eliminates numerical dispersion as a problem. A number of cases are presented in which the sensitivity of oil recovery to variations in polymer slug size, polymer concentration, polymer adsorption and brine salinity was studied. Results from these cases show that oil recovery is sensitive to these variables and that using less realistic assumptions can give significantly different results.