Stress change investigation during polymer-augmented waterflooding in channeled reservoirs

Waterflooding is by far the most widely used method to increase oil recovery; however, it is less effective in heterogonous channelized reservoirs because injected water move easily to channels and left behind most oil unswept. Polymer augmented waterflooding is a technique by which recovery is enhanced in heterogonous channelized reservoirs. Injected polymer improves conformance hence recovery by diverting flooded water into unswept portion of the reservoirs. The stress change due to polymer adsorption could be significant and need to be accounted. In this study, implicit in pressure and explicit in both saturation and polymer concentration (IMPES), finite difference numerical simulation was formulated and implemented. The implemented approach is used to study the performance of polymer augmented waterflooding by varying relevant reservoir and well parameters. Both homogenous and channel dominated heterogonous reservoir permeability cases were considered with more emphasis on channeled cases. A Langmuir adsorption as a function of polymer concentration was used to account for the irreversible adsorption of polymer during flooding. The effect of polymer adsorption on mobility and permeability was accounted for by a viscosity adjustment and residual resistance factor formulae. The stress change created as a result of polymer adsorption and pore pressure change is accounted by explicitly calculating the stress after pressure is computed from the fluid flow simulator in each iteration. From the cases considered in this study, both permeability reduction due to stress change and adsorption of polymer has considerable influence on oil recovery. Hence it is recommended to investigate these effects for any reservoirs (especially for more stress sensitive reservoirs) during screening and implementation of polymer flooding.