5 Summary
To evaluate the influence of viscosity ratio M and capillary
number Ca on relative permeability k in a two-phase flow
system, we calculated k for nonwetting and wetting fluids
(k nw and k w) under variousM and Ca conditions using an LBM simulation. The main
results of this study are as follows.
- In our simulations, the relative permeability of the nonwetting fluid
increased as the viscosity ratio increased due to the lubricating
effect and instability of the fluid interface. Specifically, at high
viscosity ratios (M = 5), k nw could
exceed 1 as a result of the lubricating effect.
- The relative permeability of the wetting fluid decreased as Mincreased due to the increase in shear drag force from the nonwetting
fluid (viscous coupling effect).
- As M increased, the Euler number of the nonwetting fluid became
higher, indicating that the nonwetting fluid became more disconnected
and formed a larger number of clusters. In contrast, the Euler number
of the wetting fluid decreased, signifying that the wetting fluid
became more connected.
- At high capillary numbers (log Ca = 0.75 to −1.25),k nw did not respond to Ca , but did so at
lower values of log Ca (<−1.25) due to the capillary
force.
- As Ca decreased k w decreased, but at a
negligible rate compared to k nw.
- k nw can change markedly in a wide range ofM –Ca parameter space, and theM –Ca –k nw correlation map
created in this study can provide k nw estimates
at various reservoir conditions.
- The color map produced from our results is useful for differentiating
effects of M and Ca when both apply simultaneously.