Oil_viscosity_dataset.zip

In this study, dispersion and mixing were studied in a steady two-phase flow generated using a co-injection method. The impact of oil viscosity was investigated over a large range of fluid viscosity ratios. The results indicate that highly heterogeneous flow fields are generated by a wide distribution of oil clusters with varied volumes. Variation in the velocity distribution enhances the deformation and spreading of a tracer plume, resulting in large dispersion scales and accelerated spreading rates. The dispersion coefficients vary with time and exhibit a non-Fickian dispersion during co-injection. Consequently, anomalous mixing behaviors can be observed when the viscosity ratio is greater than 10. The mixing strength, which is characterized by the scalar dissipation rate, is first enhanced by distortion and folding on the surface of the solute. Therefore, diffusion makes a major contribution to mixing, resulting in a faster decrease in the mixing strength in the late time regime. These results can be attributed to the fact that the non-wetting fluid becomes more disconnected and the size of each cluster decreases as the oil viscosity increases. Pore throats are narrowed by the formation of an oil film and a reversed lubrication effect of the oil film may contribute to the enhanced dispersion and mixing state, even with low relative permeability of the wetting phase. This study provides insights into dispersion in partially saturated porous media with varied oil viscosities at both the macro and pore scales, which can contribute to further improvement in CO2 storage capacity and safety.