Characterizing the thermal state and recovery potential of flooded coal mines using fibre optic Distributed Temperature Sensing methods

Mine water geothermal and thermal energy storage
offers opportunities to contribute to the decarbonisation
of heating, taking advantage of the large volume of
water stored in mining voids over extensive areas. Tens
of successful mine water heat recovery schemes are
currently operating worldwide. However, their
widespread development is hindered by the
uncertainties in assessing the resource potential and
system sustainability. In Glasgow, United Kingdom,
the UK Geoenergy Observatory (UKGEOS) has been
developed to provide an at-scale research facility to
study mine water geothermal energy. The facility
includes five mine water boreholes accessing the
flooded mine workings of the Farme Colliery, closed in
the 1930s, all equipped with Distributed Temperature
Sensing (DTS) fibre optic cables, that allows the
continuous monitoring of temperature, and provide
insights into hydrogeological and thermal processes
within the flooded galleries and surrounding rock mass.
This paper presents the results of six months of DTS
monitoring in two mine water boreholes. Data analysis
is used to characterize the thermal state of mines,
including the effect of the reservoir properties and
heterogeneities, the fluctuations linked to natural
processes and in response to heat injection-abstraction
experiments. This large-scale analysis provides insights
into the overall long-term heat and storage potential of
mines, and to the optimal design of these systems across
the world.