Dispersion of imbibition fronts

TL;DR

This study investigates how imbibition fronts disperse in porous media, revealing hyperdispersive behavior at low velocities and prewetted conditions, with dispersion characteristics strongly dependent on velocity and wetting state.

Contribution

It provides new insights into the dispersive behavior of imbibition fronts, highlighting the conditions under which hyperdispersion occurs and its dependence on velocity and prewetting.

Findings

Hyperdispersive profiles at low velocities in prewetted media.

Dispersion coefficient divergence depends on velocity.

Hyperdispersion absent at high velocities or without prewetting.

Abstract

We have studied the dispersive behaviour of imbibition fronts in a porous medium by X-ray tomography. Injection velocities were varied and the porous medium was initially prewetted or not. At low velocity in the prewetted medium, the imbibition profiles are found to be distinctly hyperdispersive. The profiles are anomalously extended when compared to tracer fronts exhibiting conventional (Gaussian) dispersion. We observe a strong velocity dependence of the exponent characterizing the divergence of the dispersion coefficient for low wetting-fluid saturation. Hyperdispersion is absent at high imbibition velocities or when the medium is not prewetted.