Characterization of hydrodynamic dispersion in porous media

The various forms of the dispersion coefficient reported to describe miscible displacement, and flow and transport of contaminants in the saturated and unsaturated zones have been explored. Dispersion has been characterized, in the oil industry, using miscible displacement experiments in saturated cores. In soil science, dispersion in the unsaturated zone has been extensively studied but yielded derivations for the dispersion coefficient which were case specific. These formulations were used to give a “rough” value of the dispersion coefficient that was then calibrated using laboratory data. A lack of generality in the derivations for the dispersion coefficient still exists. The primary reason for this is the inability to include the effects of phase saturation on the dispersion coefficient. Besides, a more confounding problem that has persisted is correlating the laboratory-scale studies with the field-scale ones where the discrepancies arise because water movement in the field is three-dimensional and not one-dimensional. Dispersion has also been characterized using statistical mechanics, but these derivations still need to be rigorously verified using laboratory and field data.