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Understanding shale behaviour is of increasing importance to the petroleum industry and also impacts on engineering issues such as landslides and hazardous waste disposal. Few data are currently available regarding geomechanical, petrophysical and dynamic elastic properties of shales that have been properly preserved and tested under controlled pore pressure conditions. The research detailed here involves triaxial testing of shales to determine failure envelopes, with ultrasonic measurements taken during the application of differential stress through to failure. Empirical relationships are then derived between the geomechanical properties and more easily (or regularly) measured physical and petrophysical properties such as porosity, clay content, cation exchange capacity and dielectric properties. The dynamic elastic properties of shales and their anisotropy are shown to be significantly impacted by maximum principal stress orientation with respect to microfabric and microfracture orientation.
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