Elastic properties of VTI and HTI shale samples as a function of stress. Laboratory measurements versus theoretical modelling

摘要

Elastic parameters and therefore the anisotropy parameters of rocks are known to be stress dependent. This phenomenon can be analysed experimentally and theoretically. The presented study investigates a full set of experimentally determined ultrasonic velocities for two shale samples with identical mineralogy under uniaxial stress conditions. The first sample has a vertical transverse isotropy (VTI) and the second sample has horizontal transverse isotropy (HTI). We apply the porosity deformation approach (PDA) according to Ciz and Shapiro (2009) on the experimentally obtained data sets and compare the change of measured elastic constants with the theoretically predicted elastic constants. Moreover, we compare the behaviour of the VTI and HTI samples with identical mineralogy under uniaxial stress. We demonstrate the applicability of the PDA for the considered good consolidated samples.