Effect of orientation of strata on macroscopic sweep efficiency of water/polymer flooding in layered porous media

Despite the available experimental and simulation studies, there is a lack of fundamental understanding of how the orientation of microscopic heterogeneities (orientation of multipermeable layers) and the placement of the injectors control the stability of the flow pattern, level of flow communication, and crossflow between multipermeable zones, polymer solution injectivity, and eventually macroscopic areal sweep efficiency of the polymer flooding in layered porous media with permeability contrast. In this study, water and polymer floods were conducted in micromodels, having three differently designed orientations of three layers with permeability contrast, to examine the effect of orientation of microscopic heterogeneity and the placement of the injectors on the above-mentioned issues. The results showed that in the early stages of the polymer injection, if the polymer solution touches the portion with the highest permeability, the macroscopic areal sweep efficiency, and thus the ultimate oil recovery, would be more efficiently improved. Also, macroscopic sweep efficiency of the polymer flooding increased with the increase in the inclination angle of the multipermeable layers, whereas waterflooding macroscopic sweep efficiency was observed to be insensitive to the inclination angle. Finally, it has been shown that the occurrence of sufficient crossflow between the zones having permeability contrast, flow pattern instability, and polymer solution injectivity is strongly dictated by the orientation of the zones with permeability contrast, proper placement of the injectors with respect to the orientation of the zones (i.e., layers), and the presence of highly conductive zones near the location of the injectors.