Pore-to-Core Characterization of Shale Multiphysics

Shale, mudstone, and claystone are fine-grained rocks that are heterogeneous at all scales and possess pore sizes ranging from nanometer to supra-micron scale. Such small sizes are not amenable to optical investigation, which has until recently prevented pore-scale investigations into shale behavior, particularly under in situ conditions. Macroscopic thermal, hydrological, mechanical, and chemical constitutive behaviors (e.g., swelling, dry-out, yield and failure, osmotic flux) are all macroscopic manifestations of pore scale, that is, nano-behavior, with nanopores containing fluid phases that differ in properties from the bulk. Characterization is not just a description of what, but needs to include an assessment of the how and why of constitutive behaviors. Recent techno-logical advances are enabling an unprecedented advancement in the characterization of shale multiphysics. This chapter examines new and ongoing efforts in shale characterization, with special attention given to in situ imaging methods. These methods are yielding unprecedented understanding of shale behavior in the subsurface and attendant responses to engineering perturbations of fluid injection, waste storage, and resource extraction including geologic carbon storage.