As we transition to a low carbon economy, alternative energy technologies need to be developed that either deliver alternative energy sources or facilitate other low carbon technologies. The shallow geosphere (<3km) has the potential to be utilised either as an energy resource, store, mineral resource or long term waste disposal site. In all of these applications, a clear understanding of the role and flow of fluids is fundamental. In the shallow geosphere, fractures and faults provide zones that facilitate the flow of fluids in the subsurface and, as such, understanding the processes effecting this movement of fluid in fractured crystalline rock is fundamental to the successful realisation of the subsurface. There are fundamental unanswered questions relating to how fluid flow in fractures changes due to induced stress, chemical and temperature perturbations in complex three dimensional fractured rock systems. The fracture networks provide the principle subsurface plumbing links to the deeper crust and the nearer surface systems, and therefore are of critical importance to the long term development of the upper crustal systems and the biosphere in general.
As part of the DECOVALEX 2023 Task G project (see https://decovalex.org/
, 2023 web site is not yet constructed), SAFENET; Safety ImplicAtions of Fluid Flow, Shear, Thermal and Reaction Pro-cesses within Crystalline Rock Fracture NETworks (SAFENET), there exists a fantastic opportunity for an innovative graduate in a natural science, computing or engineering discipline to undertake an industry sponsored PhD using world unique experimental apparatus, the GREAT cell ( https://www.ed.ac.uk/geosciences/facilities/great-cell-laboratory
), at the University of Edinburgh, and to further develop numerical modelling tools to simulate the flow of fluid under near crustal conditions of true-triaxial stress, temperature and geochemistry.
Deep geological storage/disposal of radioactive waste is a key technology, not only for the further development of low carbon nuclear power, but also to address the significant legacy of waste from past power generation. Working within the DECOVALEX program the successful candidate will have the opportunity to contribute towards this, as well as addressing fundamental questions of subsurface fluid flow such as shear reactivation of pre-existing discontinuities and the formation of new permeable pathways due to mechanical and thermal disturbances which could significantly impact the biosphere and the anthroposphere. Additionally, there are a number of applied subsurface geo-engineering fields for which the knowledge gained in the PhD will be of direct relevance, e.g. geothermal reservoir engineering, CO2 sequestration, energy storage in geo-reservoirs.
The successful applicant will be involved in undertaking coupled thermal, mechanical and chemical experiments using the GREAT cell on fractures and fracture networks in the GREAT cell under the guidance of the supervisory team. Changes to the fluid flow characteristics, such as permeability and geochemistry of the effluent, in response to temperature changes and stress changes will be investigated. Shear conditions and normal stress conditions will be established, and hydraulic stimulation conditions including pulsed hydraulic stimulation, or “soft cyclical hydraulic stimulation” will be investigated.