Compression of Porous Materials: combined ultrasonic and microtomography measurements with lattice-Boltzmann permeability simulations

Combined ultrasonic and X-ray microtomography measurements enable simultaneous investigation of elastic wave velocity (v_P and v_s), Poisson's ratio, pore structure, properties porosity, and permeability at in situ high pressure conditions. Experiments were completed using a simple analog material, porous, mold-quality aluminum, in a Paris-Edinburgh cell at Argonne National Lab, with pressures ranging from 0.14 to 1.36 GPa. Porosity was observed to have a strong inverse dependence on pressure up to 0.9 GPa, while permeability has an anisotropic dependence on pressure. Permeability decreases with pressure but is consistently lower in the direction parallel to compression than in directions perpendicular to compression. Elastic wave velocity (v_p, v_s) and Poisson's ratio increase with pressure. Measurements of v_p agree well with the Hashin-Shtrikman upper bound at lower pressures and higher porosities. These results demonstrate that a new methodology combining experimental (ultrasonic and X-ray microtomography measurements) and analytical (Lattice-Boltzmann analysis) methods provides evidence of cross-property links between microscopic structure and macroscopic elastic properties. Future investigations using more complex Earth materials may have important implications for our understanding of the composition of the deep Earth.