ABSTRACT
In rock salt, fluid transport can occur under dilatant conditions, or if fluid pressure above the minor principal stress can open pathways (pressure-driven percolation). Recently, high permeabilities in rock salt have been postulated under certain conditions, in particular, at high stresses and temperatures. We investigated fluid transport in natural rock salt drill cores at five points under supposedly permeable conditions that are plausibly relevant for a repository for heat-generating nuclear waste. Experiments included several stages of fluid pressure up to almost the confining stress, and a final fluid breakthrough phase with fluid pressure above the minor principal stress. Both nitrogen and saturated NaCl solution were used as test fluid. Fluid breakthroughs were observed at all conditions when the fluid pressure exceeded the minor principal stress. Some samples showed flow already below the minor principal stress, with permeabilities in the order of https://www.w3.org/1998/Math/MathML"> 10 − 20 m 2 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003295808/8891a5ee-2b0f-44f8-83cf-6d1fa194365a/content/inline-math19_1.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> or below, likely due to the small size and pre-existing sample damage. However, a stable permeability over longer times was not observed in any of the experiments. Intriguingly, no experiments with (wetting) brine showed any initial permeability. The claims of permeable rock salt were thus not confirmed.
