ABSTRACT:

The objective of this paper is to provide an overview of a new data-based approach to understanding and modeling strength anisotropy in porous sandstone with potential application to a wider range of geomaterials. The rationale for the contribution is the interest in quantifying the impact of mechanical anisotropy in practical industrial applications such as the prediction of mechanical behavior of hydrocarbon reservoirs during depletion or injection. The onset of yielding can have profound impact on flow and elastic properties, and it is still unclear to what extent anisotropy may affect those predictions. After recalling an extensive mechanical data set obtained previously on samples of Rothbach sandstone, we define our modeling strategy using other experimental and theoretical work from the literature. This results in the necessity of determining what an appropriate isotropic yield envelope might be. We propose an approach whereby isotropic and anisotropic models are defined and parametrized sequentially. We obtain a consistent framework where the microstructural controls on strength, including anisotropy, may be understood better than previously, allowing the revisiting of legacy data sets as well as the designing of better informed geomechanical testing programs in core analysis.

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