Thermo‐Hydro‐Mechanical Testing of Shales

The continuous growing interest for shales in numerous energy-related engineering applications brings the need for a comprehensive understanding of their geomechanical behavior and, consequently, for the establishment of sound laboratory protocols and workflows for a better characterization of these materials. This chapter discusses some recent advances in laboratory techniques and devices to characterize shales in thermo-hydro-mechanical conditions. A methodology is presented to analyze the volumetric response over time associated with the dissipation of excess pore pressure generated by loading. The partial fluid saturation of shales is introduced. Shales can become unsaturated as a result of sampling and generate suction, or they can experience changes in their degree of saturation in their natural state. Two ways to assess the water retention behavior of shales are discussed either by direct measurement of suction or by the analysis of mercury intrusion porosimetry tests. Gas injection tests are presented to study the coupled hydromechanical processes associated with gas transport. Nonisothermal testing conditions are discussed in order to measure the thermal conductivity of shales and to assess the volumetric response upon coupled thermomechanical stress paths. The chapter reports several experimental data on a variety of shales to show typical thermo-hydro-mechanical shale responses.