Application of Koval's Theory to Low Salinity Waterflooding and the Hybrid of Low Salinity Waterflooding and Polymer Flooding

Abstract

Abstract While fractional flow theory is a useful first step in modeling enhanced oil recovery, viscous instabilities and channeling often have a large impact the timing and efficiency of oil recovery, as they do in low salinity waterflooding. Jain and Lake (2013) developed an analytical method the combines fractional flow theory with Koval's method to account for these instabilities for situations when two fronts are form, and solved the resulting equations for miscible floods using the method of characteristics. We apply this method for low salinity waterflooding and the combination of polymer flooding and low salinity waterflooding. To make the method fit for the purpose of screening, we extended the theory to approximate the spreading wave of the chase flood and explain conditions for the new set of shocks that form in this application which have not been described previously. For the combination of low salinity and polymer flooding the theory is extended to add a third front. The resulting approach provides an effective screening tool for low salinity waterflooding and the combination of low salinity waterflooding and polymer flooding EOR projects which accounts for the impact of heterogeneity/mobility ratio on these floods. Application of this model to secondary corefloods gives a simple explanation for why the two fronts predicted by fractional flow theory are typically not observed. Application to tertiary corefloods demonstrates why there is often early breakthrough and a broad range of slopes in the oil recovery versus throughput. Application to Low Salinity/polymer flooding hybrid process demonstrates the full value of mobility control in overcoming unfavorable mobilities between the oil bank and chase low salinity waterflood.