MUSE pilot area activities – RESULTS – #8 Glasgow

Glasgow Observatory – A promising research and innovation location for geothermal energy with shallow mine water

A. Monaghan, K. Shorter and D. Boon (BGS), 4 August 2021

Glasgow is Scotland’s largest city and has a post-industrial landscape with a rich social and economic history bound to underground coal mining, shipbuilding and other heavy industry. The regeneration of the city and decarbonisation of old and new building stock could benefit from re-use of flooded, abandoned coal mines for low carbon heating, possibly integrated with district heating.

The Glasgow monitoring activities reported in MUSE are from the twelve UK Geoenergy Observatory boreholes between 16 – 199 m deep, constructed for mine water heat (shallow coal mine geothermal) and environmental baseline monitoring research and innovation. Borehole drilling, construction and testing took place between 2018 and 2020. Hydrogeological data loggers measuring temperature, pressure and conductivity have been installed in ten of the boreholes since August 2020. There are ongoing surface water and groundwater chemistry sampling programmes and hydrogeological test pumping has been completed.

Figure 1. Groundwater sampling during test pumping of a mine water borehole at the UK Geoenergy Observatory in Glasgow

Initial test pumping and monitoring has produced a wealth of data. For example, three boreholes in the Glasgow Upper mine workings gave a consistent transmissivity estimate (median 1020 m2/d, range 950 – 1020 m2/d) and the two boreholes intersecting the Glasgow Main mine workings give transmissivity estimates of 2000 and 2100 m2/d. Temperature measurements show that the groundwater in the deeper Glasgow Main coal mine working is warmer, at 12.4 – 12.8 ºC, than the shallower Glasgow Upper mine working and the overlying bedrock with temperatures of 11.5 and 12.0 ºC respectively.

The hydrochemistry of the groundwaters sampled during test pumping is variable. Three hydrochemical facies are identified. All the groundwaters are mineralised, near neutral pH, bicarbonate–type waters with sodium as the dominant cation, except for two boreholes with calcium as the major cation. The mine water composition is typical of Scottish mine waters reported in other studies. A detailed blog has been published on some initial results of downhole distributed sensor monitoring using fibre optic cables in the mine water boreholes. An example is in the image below that shows the natural temperature profile in one of the mine water boreholes (Oct 2020). Between 0 – 8 m below ground surface, the temperature is relatively warm (yellow colour indicates >12°C) due to the summer solar heat trapped in the shallow soil layers, known as the zone of seasonal fluctuation. Below 8 m, the temperature increases linearly with depth, in this case reaching 11.5 °C at around 55 m depth. Further measurements over longer time periods are needed to establish representative temperature ranges for the mine system, to indicate likely ground source temperatures in the wider area and to identify factors that control the local shallow geothermal gradient.

Top left: Time series image of downhole Fibre-Optic DTS-measured temperature variation through October 2020 from borehole GGA07. Top right: stacked downhole temperature plots for October 2020. Bottom: daily range and means of temperatures. Temperature unit is degrees Celsius, depth in metres.

The promising charaterisation and monitoring results have shown the UK Geoenergy Observatory in Glasgow is a representative location for at-scale research and innovation in shallow mine water geothermal energy. The Glasgow Observatory is not being used to heat buildings. It is open for use by academic and commercial researchers, engineers and innovators over the next 15 years and we would be pleased to hear from you should you wish to utilise the infrastructure for a research and development project.

References and open data

Reports and open data are available at the UK Geoenergy Observatories website.

Key reports currently published for subsurface hydrogeological monitoring include:

Shorter, K M, MacDonald, A M, Ó Dochartaigh, B E, Elsome, J, & Burke, S. 2021 Data release and initial interpretation of test pumping of boreholes at the Glasgow UK Geoenergy Observatory. Edinburgh, UK, British Geological Survey, OR/21/016. 104pp.

Shorter, K M, Palumbo-Roe, B, Fordyce, F M, Ó Dochartaigh, B, &  Walker-Verkuil, K. 2021. UK Geoenergy Observatories Glasgow: Groundwater chemistry data collected during the borehole construction phase. Edinburgh, UK, British Geological Survey, OR/21/015. 45pp.

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