IAP2-22-408

Constraining the geological evolution of the western portion of the Midland Valley: implications for its geothermal and H storage potentials

The Midland Valley of Scotland is a Palaeozoic sedimentary basin containing ‘high carbon’ resources that have been central to the economic development of the region. Recently, the basin evolution of its eastern and central sectors has been investigated and applied to the potential for low carbon geo-energy applications, including storage for hydrogen and geothermal energy (e.g. Heinemann et al., 2018; Monaghan et al. 2021; McKenna, 2022; Persano et al., 2022). These studies have demonstrated that the Carboniferous deposits of the Midland Valley (i) contain opportunities for shallow and deep geothermal, underground thermal storage and H storage and (ii) thermochronology can reveal information on large scale variations in thermal conductivity and paleo-heat flow that, coupled with provenance studies and rock properties measurements may inform the capacity and sustainability of geo-energy resources. The project proposed here focuses on the central-western sector of the basin, the geological and thermal history of which has been poorly constrained due to lack of seismic and deep well data, and its potential as a ‘renewable geo-energy’ play opportunity are poorly known. The study will use a series of techniques to constrain the geological history of the basin, the evolution of its thermal structure and rock properties to assess areas particularly suited for their economic potential.

Methodology

Several methods will be used to fulfil the aims of this project. The student will investigate the available geological maps and boreholes to assess areas where the Palaeozoic rocks are best exposed. A careful fieldwork will assess the nature of these rocks, which include sedimentary deposits and igneous intrusion, their stratigraphic relationship and their suitability for low temperature thermochronological studies. The field areas can be reached quickly from Glasgow and they are easily accessible. Samples will be collected for obtaining double dating in the apatite and zircon crystals, to constrain both the provenance of the sediments and the age of the intrusions (U/Pb ages on apatites and zircons) and the thermal evolution of this portion of the basin (apatite and, potentially, zircon fission track thermochronology). The data will be obtained using a LA-ICPMS hosted at the University of Glasgow. The interpretation of the data will be performed using QTQt, a software that allows for thermal histories to be reconstructed, including the evolution of the geothermal gradient through time. Rock properties such as porosity, permeability, thermal conductivity will also be measured and petrographic descriptions will be made to understand the diagenetic history. Stratigraphic, sedimentological, thermochronological data will be then combined in a 2D model (to be codified by improving an already available 1D version) to assess the potential of the basin as a play opportunity for H storage and geothermal energy, including how sustainable significant heat abstraction or repeated gas cycling may be.

Project Timeline

Year 1

Literature review, fieldwork, sample collection. The student will also become familiar with thermochronological analyses

Year 2

Thermochronological analyses; the student will perform all the analyses in person, under the supervision of Drs Persano and Wildman, acquiring expert knowledge in microscopy (optical and SEM) and mass-spectrometry (LA-ICPMS). Preliminary interpretation of data; participation to a national conference. Fieldwork to assess possible shortcomings of the first season. Visit to Prof. Gallagher (University of Rennes) who codified the software QTQt to improve an already available 1D model of the thermal structure of the crust to construct a 2D model.

Year 3

Data production and interpretation. Presentation of the project at at least 1 international conference (e.g. EGU); the PhD thesis may be written as a collection of three papers.

Year 3.5

Completion of the thesis

Training
& Skills

Specific training: sedimentary logs and stratigraphic reconstructions. Low temperature thermochronology, microscopy, mass-spectrometry, thermal modelling. Rock property measurements and thin section petrography. Transferrable skills: oral and written communication; project management, working independently and in teams; time management.

References & further reading

Heinemann, N. et al.. 2018 Hydrogen storage in porous geological formations – onshore play opportunities in the Midland Valley (Scotland, UK). International Journal of Hydrogen Energy, 43; 20861-20874
Monaghan, A et al. 2021. Drilling into mines for heat: geological synthesis of the UK Geoenergy Observatory in Glasgow and implications for mine water heat resources. QJEGH, https://doi.org/10.1144/qjegh2021-033
McKenna E. 2022 The provenance and thermal histories of the Carboniferous Midland Valley of Scotland. PhD thesis (available online from the University of Glasgow library)
Persano C et al. 2022 Geology, geochronology and geoenergy of sedimentary basins: insights from the Midland Valley of Scotland, UK. EGU General Assembly 2022, Vienna, Austria, 23-27 May 2022, EGU22-8433

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