Percolation in Salt Rocks - 18652

We present laboratory investigations of fluid percolation in salt rocks, performed on drilled core samples, which show that natural rock salt does not become permeable at high pressures and temperatures, as had been claimed in the literature. Rather, we confirm the existence of a percolation threshold: Fluid migration is only possible when the fluid pressure equals or exceeds the lowest confining stress. The lab tests corroborate in-situ-determinations of the percolation threshold in salt formations: The threshold is given by the minimal stress in the rock mass (minimal stress criterion), and fluid pressure-driven percolation starts once it is exceeded. The hypothesis that the percolation threshold vanishes at high pressure and temperature is thus refuted by experiments on natural rock salt. These experimental tests, performed in the framework of the KOSINA project, are an important prerequisite for the proof of integrity of saliferous barriers in the disposal of radioactive waste in salt rocks. (authors)