Multiphysical Behaviour of Shales

The involvement of shales in new energy-related fields such as the extraction of gas shale and shales oil, the deep geothermal energy capture, the sequestration of CO2 and the nuclear waste geological storage, has raised a new and growing interest in the geomechanical behaviour of the material. In this context, fundamental issues come along with the complex multiphysical conditions in which the geomaterial is found where temperature, chemistry and unsaturated conditions play a major role. As a consequence the study of the coupled thermo-hydro-chemo-mechanical (THCM) behaviour of shales is strongly sought. This lecture introduces the most recent advances in the experimental testing and modelling of the THCM behaviour of shales. Such testing under complex multiphysical conditions come along with the need to develop advanced experimental tools and techniques to reproduce the extreme multiphysical conditions experienced by shales in the context of the latest engineering developments. The lecture addresses the devices developed and methodologies established to study the water retention properties of shales and gas shales, the water and gas transport properties, the 1D volumetric behaviour, the thermo-mechanical couplings, the impact of the pore water composition on the mechanical response and the unsaturated behaviour of shales. A workflow established for the analysis of the water retention behaviour of shales in non-isochoric conditions is introduced; the method allows for the determination of the main drying and wetting paths and of the volume change response upon total suction variations (Ferrari et al. 2014)