Researchers working at the UK Geoenergy Observatory in Cheshire have shown that distributed acoustic sensing (DAS) has the potential to detect subsurface temperature change during geothermal experiments. The research, which was conducted by scientists from the University of Leeds as part of the NERC-funded SmartRes project (grant number NE/X005496/1), used a high-resolution, fibre-optic DAS sensing system installed in boreholes at the Cheshire Observatory.
During two days of surveying in June 2025, over 1000 seismic impacts were made at the ground surface using a controlled seismic energy source. The energy generated by these impacts essentially sound waves propagating through the ground was recorded by DAS in the 5 km fibre-optic network installed in the observatory's 100 m-deep boreholes. Strong seismic arrivals were visible at all depths, validating the survey set-up and providing an encouraging seismic baseline for future thermal testing. During subsequent tests, researchers will measure whether any variations in the arrival time of sound waves can be detected, as this could indicate where heat is moving in the subsurface.
DAS sensing has proven its credentials in many subsurface settings, but is yet to be widely developed for monitoring shallow geothermal operations. Initial analysis of the data recorded in Cheshire confirms the potential of this technology to provide high-resolution monitoring of the Sherwood Sandstone Group aquifer. This will contribute to wider understanding of geothermal processes and help with the design of efficient heating systems that use geothermal energy. The measurements are one of several datasets that provide a baseline for the acoustic, electrical and thermal properties of the Sherwood Sandstone Group.
Seismic energy recorded by DAS fibre-optic cable in borehole TH0422 at the Cheshire Observatory site. The cable reaches 100 m below ground level before returning to the ground surface, hence the symmetry in the seismic arrival pattern. Changes in the arrival time of seismic energy during thermal testing may be correlated with thermal change in the Sherwood Sandstone Group. © Adam Booth/SmartRes.
It's been very exciting to undertake the first DAS survey at the Cheshire Observatory. Fibre-optic technologies like DAS are giving us unprecedented insight into many subsurface processes. For geothermal applications, the insight is really timely: we need to demonstrate to prospective stakeholders that we understand how subsurface properties will evolve under various heating scenarios.
Prof Adam Booth, associate professor of applied geophysics at the University of Leeds.
The UK Geoenergy Observatories have been designed to advance our understanding of energy storage in shallow geological systems. This cutting-edge research undertaken by the team at the University of Leeds is an excellent demonstration of the potential for these facilities to deliver on that promise.
Dr Mike Spence, science and operations lead at BGS for the Cheshire Observatory.
The UK Geoenergy Observatories are a network of custom-built facilities operated by BGS that were designed to enable research in shallow geothermal energy and underground thermal energy storage. The facilities are available to the UK science community for research, innovation and training activities.
For further information, including details on how to access the sites, please visit the UK Geoenergy Observatories website.
