Experimental and Numerical Characterization of Lower Huron Shale as a Heterogeneous Material

Understanding mechanical properties of organic rich shale is crucial for successful exploration and long-term production of hydrocarbons from unconventional reservoirs. Due to the organic matter and clay minerals interlaced with other silicate minerals, shale can be studied as a heterogeneous material. In this work, the average mineral compositions and elastic mechanical properties were first characterized by scanning electron microscope, energy-dispersive X-ray spectrometer, and atomic force microscopy. Uniaxial compression and triaxial compression tests were then conducted on core-scale Lower Huron Shale samples. Numerical models were constructed to extract mechanical properties from both uniaxial compression and triaxial compression experiments. Next, homogeneous, mineral-based, and Weibull distribution-based numerical models were developed to investigate the influence of the mineral heterogeneity and shale hydration effect on the strength and deformation behavior of shale rocks. The homogeneous models have higher compressive and tensile strengths as well as mechanical properties than heterogeneous models. Compared to homogeneous models, when the shale rock is simulated with heterogeneous models, a transformation from brittle to ductile in stress-strain responses and that from simple modes to complex modes in failure mechanisms are observed. It is also demonstrated that the mineral property distribution and shale hydration effect have a larger influence on the triaxial compression strength. Furthermore, simulation studies suggest that numerical models accounting for the heterogeneity of shale can improve the accuracy of the mechanical property characterization. The outcome of this research will benefit the understanding of the Lower Huron Shale mechanical properties, which has significant implications to the successful development of shale reservoirs.