Mineral scaling of fracture fluid pathways in geothermal reservoirs – an experimental approach


  • Supervisors: Dr David McNamara, University of Liverpool
    Prof. Yan Lavallée, University of Liverpool
    Prof Dan Faulkner, University of Liverpool

  • External Supervisors: Professor Sandra Piazolo, University of Leeds

  • Contact:

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

  • CASE Partner:

Application deadline: 10 January 2020

Introduction:

Fracture scaling is an important aspect of the crack-seal cycle, the mechanism by which Earth’s crust destroys and heals itself. Tectonic forces generate fractures allowing fluids to circulate in the crust. As fluids travel through fractures mineralisation occurs resulting in fracture scaling. Controls on fracture scaling, including environmental conditions and atomic, physical processes that facilitate mineral formation are underexplored, highlighting a fundamental research gap in geological science. This research gap is a barrier to fully understanding how fractured geological systems behave over time, and to our ability to develop and utilise techniques that promote or hinder fracture scaling in geological systems important for renewable, geothermal energy development. Development of natural and engineered geothermal resources increased in recent years and is a key target for renewable energy development in Europe. The successful development and longevity of fractured geothermal resources relies on establishing and maintaining open fracture networks in hot reservoir rocks to allow circulation and extraction of geothermal fluids. Fracture sealing in such systems is thus deleterious to their sustainability (McNamara et al., 2016; Griffiths et al., 2016). Utilising expertise and state-of-the-art facilities at the University of Liverpool this research project will simulate fracture mineral scaling in the laboratory across a range of known geothermal conditions and a range of fractured geothermal reservoir rocks, and use nano-microanalytical techniques to compare synthetic material generated by these experiments to natural examples of sealed geothermal fractures from New Zealand and Iceland geothermal systems.

Project Summary:

The proposed research aims to:

1) Generate synthetic sealed fractures in the laboratory under relevant geothermal conditions and with variable fluid compositions to determine controls on the rate of fracture sealing.

2) Carry out nano-microanalytical techniques on synthetic sealed fractures to determine physical controls on mineral scaling nucleation and growth and link these to experimental conditions.

3) Compare nano-microstructural data from lab generated material to natural examples of sealed geothermal fractures from New Zealand and Iceland to test a) the appropriateness of laboratory techniques, and b) provide novel information on the evolution of these natural geothermal systems.

References:

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.

Sonney, R. and Mountain, B.W., 2013. Experimental simulation of greywacke–fluid interaction under geothermal conditions. Geothermics, 47, pp.27-39.

Griffiths, Luke, M. J. Heap, Fei Wang, Damien Daval, H. A. Gilg, Patrick Baud, Jean Schmittbuhl, and Albert Genter. "Geothermal implications for fracture-filling hydrothermal precipitation." Geothermics 64 (2016): 235-245.

Walker, R. J., Holdsworth, R. E., Armitage, P. J., & Faulkner, D. R. (2013). Fault zone permeability structure evolution in basalts. Geology, 41(1), 59-62.

Lamur, A., Kendrick, J. E., Eggertsson, G. H., Wall, R. J., Ashworth, J. D., & Lavallée, Y. (2017). The permeability of fractured rocks in pressurised volcanic and geothermal systems. Scientific reports, 7(1), 6173.

Apply Now