Cheshire Geoenergy Observatory gears up for debut

The UK Geoenergy Observatory in Cheshire is nearing completion; drilling has been completed and the surface infrastructure is now being installed.

The Cheshire Observatory, located in the University of Chester’s Thornton Science Park, will provide scientists with at-scale test facilities that can be used to optimise and de-risk a range of subsurface energy technologies, including geothermal energy.

It is part of the £31 million UK Geoenergy Observatories project, led by the British Geological Survey (BGS), which has also delivered an observatory in Glasgow for the investigation of mine-water heat and a core scanning facility at BGS Keyworth.

Construction has been in progress since July 2022, informed by technical advisors Ramboll and led by AECOM as principal contractor. With the construction phase coming to a close the observatory is set for an official opening in spring 2024.

3D mapping of heat and fluid flow

A closely spaced array of 21 boreholes has been drilled to enable researchers to map thermal transport through the Observatory rock volume. The close spacing of the boreholes ensures that heat and fluid flow can be related to specific geological features such as faults, fractures, pebble beds and sandstone permeability.

Ground truth is provided by over 1000m of drill core and geophysical wireline log data, and a dense array of sensors has been installed to monitor temperature and rock properties in close to real time. Installation of the borehole array involved 10 months of drilling within a 36 x 36m area and to a depth of 100m. This necessitated very careful planning and close monitoring of borehole verticality.

Data from borehole monitoring systems activated during the construction phase has highlighted important flow paths within the aquifer, which will be key targets for transport research in the operational phase. Open fractures in the sandstone created interesting challenges for the drilling team as they worked out how to avoid modifying them by enlarging them, clogging them with sediment or allowing grout to migrate along them.

Reports detailing the design and construction of the Cheshire Observatory, together with during-drilling monitoring and commissioning datasets will be shared openly online in due course.