oa Empirical Correlations to Shale Strength

A suite of preserved shales from basins widely separated in space and time underwent multi-stage triaxial tests in the laboratory to evaluate static and dynamic mechanical properties. Coupled with these tests was a workflow for extensive characterisation of physical and petrophysical properties, including porosity, bulk density, specific surface area, electrical properties and microstructural evaluation. Good correlations have been found between shale strength (cohesion and unconfined compressive strength) and some physical properties and there are encouraging relationships between dielectric properties and both static and dynamic mechanical properties. Poor relationships were found to friction coefficient and also between properties previously thought good for predicting shale strength, such as P-wave velocity.