Abstract
A complete set of anisotropic poroelastic parameters for Berea sandstone at low TERZAGHI effective stress (confining stress minus pore fluid pressure) was obtained for a series of drained, undrained and unjacketed tests using a triaxial vessel. Thirty-six stress-strain and stress-pore pressure slopes were obtained from hydrostatic and uniaxial experiments on three samples whose orientations were parallel, perpendicular, and forty-five degrees to the bedding plane. Stressstrain slopes during hydrostatic experiments indicated that the sandstone's poroelastic behavior was transversely isotropic. A non-linear least-square fitting technique was applied to obtain the complete set of poroelastic parameters. Results show that the sandstone is poroelastically anisotropic at low TERZAGHI effective stress conditions but it is reasonable to assume micro-isotropy. Volumetric compliances obtained from this result with that from previous measurements, which assumed that the sandstone was isotropic, were consistent between each other.
This technique gives us internal consistency checks and a measure of the reliability of the values, and it yields a more reliable set of poroelastic constants.
