Acoustic wave propagation and permeability in sandstones with systems of aligned cracks

Abstract

Abstract A polyaxial (true triaxial) stress-loading system has been developed for testing cubic specimens of rock, with the capability of varying each of the principal stresses independently. Facilities are incorporated for measuring all nine components of P and polarized S-wave velocities and attenuation in the principal directions, and for fluid permeability in the 1-direction. Tests have been performed on specimens of five sandstones, in which systems of aligned cracks have been introduced by increasing σ 1 and σ 2 together to near failure, while maintaining σ 3 constant at some low level. Results indicate that there are excellent correlations between permeability in the plane of the aligned cracks as they are closed under hydrostatic stress and both velocities and attenuation of (1) P and S waves propagating in a direction normal to the plane of the cracks, and (2) S waves propagating in the plane of the cracks and polarized normal to the plane.