Gas Permeability of Granular Salt During Consolidation

Gas permeability measurements have been made on granular samples during consolidation under hydrostatic stresses up to 40 MPa and temperatures up to 250 °C. The initial porosity of the samples prior to consolidation was as great as 0.40; depending on the test conditions and duration, the resulting final porosity was between 0.08 and less than 0.01. Although these tests were conducted at different temperatures, pressures, durations and salt types, a similar reduction in permeability was observed. The permeability steadily decreased from the initial relatively large value around 10^-14 m² until after some critical porosity is reached (between 0.02 to 0.05); below the critical porosity, the permeability decreased at an increased rate. This response is attributed to loss of pore connectivity within the consolidating salt sample. The data suggest a very low porosity will have to be reached before the permeability of consolidating granular salt will be comparable to intact salt for conditions considered here.