Dynamic dissolution of halite rock during flow of diluted saline solutions

The dynamic dissolution pattern of halite salt rocks taken from coreholes near the Dead Sea was studied in laboratory-scale experiments. When unsaturated solution (with respect to halite) flowed through salt cores, dissolution developed along preferential flow pathways in a channel structure. The channel structure was related to the salt's properties and internal heterogeneities, flow velocity and impact of gravity. Preferential dissolution pathways developed in areas of minimum resistance to flow, such as large-pore networks and cracks. Nevertheless, in many cases no structural heterogeneity was observed along the dissolution channels prior to the experiments. The initial formation of channels took place above a critical flow velocity; below this threshold, dissolution developed as a slowly propagating front. In these cases, salt re-precipitation resulted in clogging and cessation of flow through a few of the salt cores. Solution density was found to be important, as evidenced by the fact that more channels developed upward than downward, due to gravitational fractionation. The development of dissolution channels could have very important implications for the overall permeability of the salt layer in general, and the use of salt formations for industrial waste storage and the development of sinkholes along the Dead Sea shore in particular.