CEE Seminar: Tailoring the Behavior of Geomaterials to Design Sustainable Geo-energy Infrastructures

Abstract: The analysis and optimum design of energy-related geo-systems - like deep geothermal energy and unconventional fossil fuel reservoirs, energy and waste geo-storage facilities and energy piles - require understanding of geo-materials’ behavior under unprecedented conditions. Particularly, their coupled hydro-thermo-mechanical response must be better understood given their complex internal structure interacting with fluids and under extreme temperatures, high stresses and various loading rates.

In the first part of this talk, I will briefly review the fundamentals of heat conduction in continuum and discrete materials and propose approaches to quantify and tune the thermal conductivity of composite two-phase granular samples. A high heat capacity, enhanced thermal conductivity, and relatively high fluid conductivity are needed in geotechnical heat storage facilities. Conversely, grains and fluids can be selected properly to attain very low thermal conductivities to create mechanically sound thermal barriers in the foundation of a heat storage facility. In this study, the evolution of the bulk thermal conductivity and compression index of engineered particulate composites are quantified as one or more governing parameters such as fabric (grain shape, mean size and size distribution), mineralogy, stress level, and pore fluid.

In the second part of this talk, I will share the results of our experimental and numerical studies on the behavior of natural rocks when subjected to hydraulic fracturing. Hydraulic fractures open the rock structure so that heat and mass recovery from rocks with low permeability is enhanced. In this study, shale rock specimens are loaded to high-stress in-situ conditions (3 km depth, plane strain) and are hydraulically fractured in the laboratory. The characteristics of hydraulic fractures and their interactions with the rock’s natural fractures are recorded with state-of- the-art optic and electromagnetic imaging techniques and analyzed via digital image correlation. These physical and numerical simulations highlight the fabric and boundary condition-dependent hydro-mechanical response of natural rocks that can be tailored for our benefit if designed properly.

Bio: Shahrzad Roshankhah, Ph.D., is a postdoctoral scholar at the California Institute of Technology, Department of Mechanical and Civil Engineering. Inspired by unprecedented challenges facing our era on energy and the environment nexus, and ample opportunities for geo-engineers to solve them, Roshankhah is passionate about developing more accurate models for the hydro-thermo-mechanical behavior of geomaterials at extreme conditions (high-temperatures, -stresses and -fluid characteristics). At Caltech, she studies the propagation of hydraulic fracture in pre-fractured rocks through experimental and numerical simulations. She also studies the elastoplastic behavior of particle impacts in granular flows and thermal properties of engineered particulate materials, which are important for the geotechnical resource recovery and storage. She has worked in engineering consulting companies for four years, where she analyzed and designed buildings and geo-structures. Roshankhah is the recipient of several educational, research and leadership awards and certificates (e.g., from NSF, GaTech and Caltech) and has served on committees as a technical reviewer for specialized symposia, as a judge for scholarship distribution, and as a mentor for broadening the participation in STEM fields. Roshankhah received her doctorate in geotechnical engineering from the Georgia Institute of Technology in 2015.