ABSTRACT:

In this study, we investigate through lab measurements, the mechanical anisotropies of a sample of calcareous shale from Duvernay Formation, Alberta. The elastic properties of the materials are measured acoustically with ultrasonic pulses transmitted through the samples. Samples are cut into prisms allowing piezoelectric (PZT) ceramic wafer to be directly attached to measure P and S wave velocities at a set of strategic angles to the material's symmetry in order to obtain the full set of material constants concurrently. The beam ‘skew’ effect in the anisotropic material is a recurrent issue in the analysis of such data. Particular efforts are taken to account for this through beam modeling and the additional receiving transducers. The measurements are conducted on ‘dry’ jacketed samples to confining pressures of 180 MPa with no attempt at control pore pressure. For reference, the maximum in-situ stress in the Duvernay Formation is estimated to be less than 150 MPa at 3000 m depth. The five stiffness essential to describe the engineering behaviors of these materials are subsequently obtained and evaluated.

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