In situ electrical conductivity measurements of porous water-containing rock materials under high temperature and high pressure conditions in an autoclave

This study presents a method for measuring the electrical conductivity of porous rock materials in situ under a shallow Earth crust environment simulated according to temperature, confining pressure, and liquid water saturation in a high-temperature autoclave. The sample was first encased within a poly tetra fluoroethylene container with two Pt wires leading out and was then placed into the high-temperature autoclave. The lead wires were connected to an external measurement system after passing through the autoclave sealing plug. The electrical conductivity of sandstone was measured under different temperatures (30, 60, 90, 120, 150 °C), liquid water saturation levels (36%, 51%, 100%), and 2 MPa by using this method. The electrical conductivity of the sandstone samples increased with increasing temperature and also increased as the level of water saturation increased. All the results agreed well with the Arrhenius relationship, Archie’s law, and previous experimental study. This method can be used to measure other kinds of porous water-containing rocks, and the results can be applied in geothermal/oil research.