Oil recovery modeling of macro-emulsion flooding at low capillary number

• Macroscopic model of oil displacement by emulsion injection based on Kr curves.
• Pore-level displacement efficiency influences oil recovery more than mobility control.
• Emulsion injection benefits are obtained even in favorable mobility ratio scenarios.
• Early emulsion injection leads to uniform sweeps and accelerates oil production.

Emulsion flooding has been shown to offer a significant potential as an enhanced-oil recovery (EOR) strategy. Moreover, recovery mechanisms of several chemical EOR methods, including alkaline and alkaline-surfactant flooding applied to heavy oil, are linked to in situ formation of emulsions. To enable emulsion flooding designs, EOR mechanisms must be adequately represented in reservoir simulators to upscale pore-level effects to the continuum in porous media. In this work, we have incorporated two known effects of emulsion flooding, namely an increased pore-level displacement efficiency and a macroscopic mobility control through changes in relative permeability curves. To this end, we used three types of emulsion and oil relative permeability curves: (1) through history matching of unsteady-state emulsion flooding data; (2) from direct use of Darcy law on steady state two-phase flow experiments; and (3) synthetic curves at which pore level displacement efficiency is characterized by the curve end-point saturation and the macroscopic sweep efficiency by the water curve end-point. A parametric analysis of a 1/4 of a 5-spot geometry shows that the displacement efficiency effect is predominantly responsible for the incremental oil recovery observed experimentally. The results also indicate that the amount of oil recovered depends on the complete relative permeability curves, and not only the end-point values. These findings imply that properly designed emulsions should produce significant recovery benefits.