Oil and Water Interactions during Low-Salinity Enhanced Oil Recovery in Water-Wet Porous Media Ryoichi

The role of emulsions should be an important factor in additional oil recovery during low-salinity water flooding (LSWF); however, it has been rarely discussed in previous studies. In this study, the contributing behavior of the oil/water interaction to the oil recovery process was investigated through core- and microscale experiments involving high-polar-component oil. Two tertiary coreflood experiments with high- and low-salinity water were conducted using cores from the same reservoir formation, where the behavior of oil recovery and that of differential pressure differed significantly. The results of core and water analyses indicate that the emulsions predominantly caused this difference. Thus, microfluidic experiments were conducted to visualize the emulsion-based oil recovery mechanisms; two phenomena of emulsions contributed to oil recovery: pore blockage and microwater dispersion. In addition, we studied the stability of emulsions in terms of the surface electric charge through the use of zeta potential measurements; emulsions were more stable in the lower salinity and higher pH conditions. These experimental results demonstrate that emulsions are important during LSWF for additional oil recovery in water-wet porous media.