Investigating the mechanical behavior of shale: A micro-scale approach

Hydrocarbon production from unconventional shale-gas reservoirs has increased dramatically in the last decades, and a good understanding of the mechanical behavior of the reservoir rock is of crucial important. Characterization of shale is challenging because this rock exhibits a multi-scale heterogeneity, and thus an improved experimental insight into the deformation and damage mechanisms at micro-scale is required. In this context, an innovative experimental approach, consisting of uniaxial compression tests in environmental scanning electron microscopy (ESEM) and full field strain measurement by digital image correlation (DIC) techniques, is proposed. Some preliminary results from two tests on samples with distinct water contents (i.e., one is dry and the other is wet) are presented. The results show that the microstructure plays a decisive role in the macroscopic properties of shale. Moreover, the mechanical properties of shale is strongly affected by water content.