In situ rock salt permeability measurement for long term safety assessment of storage

Abstract A field test was carried out in the Amelie Mine owned by Mines de Potasse d'Alsace (MDPA, France) for the purpose of measuring rock salt permeability away from underground facilities. The selected salt bed is about 1 m thick and located 16 m away from the gallery floor. The permeability was measured by means of nitrogen and saturated brine injection. Theoretical studies indicated that in order to control the `disturbing effects' (thermal effects, chemical reaction between halite and brine), the work should be done at constant temperature and pressure. The field experiment results confirm that rock salt is permeable to gas and brine, even relatively far from underground openings. The measurements of the tests with brine were interpreted satisfactorily by a model based on Darcy's law, with an intrinsic permeability value of 2×10 −21 m 2 and an initial pore pressure value of 1 MPa. Interpretation of the measured gas flow rate shows that: (a) after brine percolation, the capillary pressure effect is significant and (b) gas migration in salt is not controlled by Darcy's law; the Knudsen effect and partial saturation may play an important role.