Miss Nadia Sonia Narayan
|PhD in the Department of Earth Sciences|
Title: Deep Palaeozoic Karst - Geothermal Potential in Britain
The UK is currently facing two pressing challenges; energy security and high energy bills. The nation has been a net energy importer since 2004, with an astonishing 48% of energy consumption attributed to heat use. Gas is the primary contributor towards domestic heat production and despite a fall in gas prices in 2015, the overall household expenditure for heating remained unchanged. This has been attributed to a greater demand in response to colder weather conditions. A convincing solution to combat the challenges we face is deep geothermal energy exploration – an essentially low carbon, renewable energy option that could deliver up to 100GW of heat to the nation. Several potential resources in deep Triassic sedimentary basins and radiothermal granites were first identified during the nationwide geothermal assessment, following the 1973 oil crisis. As a result, the deep geothermal well in Southampton (the first of its kind in the UK) was established, encountering 76°C brines at a 1.8km depth. Further ventures have since been undertaken, with resources identified at Eastgate in the Weardale granite (46°C encountered at a 995m depth); Ardwick in Manchester’s Carboniferous limestones (134°C estimated at 4150m) and at the Eden Project in south-west England’s granites (180-190°C waters predicted at 4km), to name a few.
Whilst the geothermal assessment of the late 1970s to 1980s conclusively established economically viable resources in Permo-Triassic strata, the Palaeozoic preceding this was neglected. This project aims to resolve this by focussing on a nationwide assessment of the Lower Carboniferous Limestone unit, which is known for its extraordinary susceptibility to develop karst features (dissolution features exclusive to limestone) – as evidenced by the limestone pavements and cave features across the British Isles. In fact, the limestone is known to host some of the longest, interconnected cave systems in Britain. Combined with the well-known fact that the limestone is known to accommodate thermal waters at depth (~45°C waters at Bath Spa have been heated to over 65°C at a 2.5km depth), this highlights the reservoir’s potential as a permeable reservoir capable of transmitting hot waters at sufficient depths for geothermal use.
The project will aim to employ the following methods, with the objective of establishing the total available resource in karstified Carboniferous Limestones across the Britain:
1) Assess the likely distribution of karst development at depth via onshore 2D seismic interpretation of unconformities.
2) Assess the temperature at depth via geothermometry analysis of spring water data, analysis of well data and literature sources.
3) Analyse flow rate from well data and literature sources
4) Analyse drill-core in the reservoir with respect to mineralogy and secondary porosity evaluations.
5) Investigate mineralogy and chemistry of tufa/travertine deposits.
6) Create a geothermal resource inventory for the Carboniferous Limestone.
- Geothermal Energy
- Narayan, N., Adams, C., & Gluyas, J. (2021). Karstified and fractured Lower Carboniferous (Mississippian) limestones of the UK; a cryptic geothermal reservoir. Zeitschrift der Deutschen Gesellschaft für Geowissenschaften - Journal of Applied and Regional Geology, 172(3), 251-265. https://doi.org/10.1127/zdgg/2021/0288