Exploring combined geothermal power and mineral extraction potential of the Galway granite complex


  • Supervisors: Dr David McNamara, University of Liverpool
    Prof. John Wheeler, University of Liverpool
    Prof Dan Faulkner, University of Liverpool

  • External Supervisors:

  • Contact:

    Dr David McNamara, University of Liverpool, d.mcnamara@liverpool.ac.uk

  • CASE Partner:

Application deadline: 10 January 2020

Introduction:

Geothermal energy has potential for meaningful contributions to decarbonize the global energy future. Numerous potential geothermal sites have been identified in the UK and Ireland in proximity to igneous bodies e.g. United Downs project, and the Galway granite. Preliminary and ongoing research has identified development potential from these resources for projects that vary from district heating, direct use (e.g. agricultural drying, aquaculture, greenhouse heating), power production, and combined metal extraction, though development of these resources remains in its infancy. In order to advance geothermal progress both nationally and internationally, further research into how granite systems operate as a geothermal fluid-flow network is required with the aim of de-risking future development. The potential of the Galway granite with regards to geothermal energy, has been investigated in the past through detailed MT geophysical surveys, and temperature analyses. A heat flow of 67 mW.m-2 was calculated from boreholes, while the overall modelled temperature at 2,500m was calculated at ~100°C, potentially rising to 129°C at depths of 5000m. Hydrothermal fluids have been transported through the granite fracture network as evidenced by quartz-ore mineralisation in faults and fractures. Detailed analysis of the structural network, modelling of contemporary flow within this network, and studying ore mineral genesis in this rock body would assist in derisking any future development of it as a resource and provide important information on the nature of such granite bodies as a resource target across the British Isles.

Project Summary:

The proposed research aims to: 

1) Map and structurally characterize the conduit fault zones and fracture networks within the Galway granite and the country rock in the area surrounding it. This will be achieved through a combination of field mapping and drill-core logging in collaboration with SLR Consulting and MOAG.

2) Combine detailed structural studies of outcrop and drillcore with structural insights from existing regional geophysical studies.

3) Generate a 3D structural and geological model of the Galway granite region that will be utilised to construct a 3D geocellular model to better understand permeability distributions within these granite bodies and to perform flow-simulations.

4) Utilise microanalytical techniques such as EDS and EBSD to understand mobilisation of ore minerals within the Galway granite in order to determine their extraction potential under geothermal operation.

References:

Farrell, T., Muller, M., Rath, V., Feely, M., Jones, A., Brock, A. (2015). IRETHERM: The geothermal energy potential of radiothermal granites in a low-enthalpy setting in Ireland from magnetotelluric data. Proceedings 2015 World Geothermal Congress.

McNamara, D. D., Lister, A., & Prior, D. J. (2016). Calcite sealing in a fractured geothermal reservoir: Insights from combined EBSD and chemistry mapping. Journal of Volcanology and Geothermal Research, 323, 38-52.

Massiot, C., Nicol, A., McNamara, D.D., & Townend, J. (2017). Evidence for tectonic, lithologic, and thermal controls on fracture system geometries in an andesitic high‐temperature geothermal field. Journal of Geophysical Research: Solid Earth, 122(8), 6853-6874

Feely, M., McCabe, E., & Kunzendorf, H. (1991). The evolution of REE profiles in the Galway Granite western Ireland. Irish Journal of Earth Sciences, 71-89.

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