The most common oil recovery method used for displacing oil and maintaining the reservoir pressure is water injection. However, in most cases, the recovery efficiency of this method is limited by the high fluid mobility ratio and reservoir heterogeneities that limit the macroscopic efficiency of reservoir sweep and pore scale oil displacement.

The non-linear flow behavior of complex fluids through porous media gives rise to multiphase flow displacement mechanisms that operate at different scales, from pore-level to Darcy scale. Experiments have shown that injection of oil-in-water emulsions and viscoelastic polymer solutions can be used as an effective enhanced-oil recovery (EOR) method, leading to substantial increase in the volume of oil recovered. The mechanisms responsible for increasing the recovery factor in different EOR methods are not fully understood.

Here, we summarize recent pore-scale studies on oil displacement by oil-water emulsion and viscoelastic polymer solutions. Visualization of the flow of complex fluids through a transparent network of micro-channels, which serves as a model of a porous media, reveals that the non-linear flow behavior improves the pore-level displacement efficiency, leading to lower residual oil saturation.

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