Abstract:
Viscous fingering is ubiquitous in miscible displacements in porous media, in
particular, oil recovery, contaminant transport in aquifers, chromatography separation, and
geological CO2 sequestration. The viscosity contrasts between heavy oil and water is several orders
of magnitude larger than typical viscosity contrasts considered in the majority of the literature. We
use the finite element method (FEM)-based COMSOL Multiphysics simulator to simulate miscible
displacements in homogeneous porous media with very large viscosity contrasts. Our numerical
model is suitable for a wide range of viscosity contrasts covering chromatographic separation as well
as heavy oil recovery. We have successfully captured some interesting and previously unexplored
dynamics of miscible blobs with very large viscosity contrasts in homogeneous porous media.
We study the effect of viscosity contrast on the spreading and the degree of mixing of the blob.
Spreading (variance of transversely averaged concentration) follows the power law t
3.34 for the blobs
with viscosity ∼ O(102
) and higher, while degree of mixing is found to vary non-monotonically with
log-mobility ratio. Moreover, in the limit of very large viscosity contrast, the circular blob behaves
like an erodible solid body and the degree of mixing approaches the viscosity-matched case.
