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Baseline Seismic Monitoring Survey for UKGEOS Glasgow Geothermal Production Using DAS

Description: 

The UK Geoenergy Observatories (UKGEOS) site in Glasgow has initiated a project to repurpose an abandoned coal mine as a shallow geothermal testbed to investigate its potential as a head source and sink. During the site construction, fibre-optic cables were installed along the 50- to 100-meter-deep boreholes that will be used for injection and extraction of water, providing a unique opportunity to examine the applicability of Distributed Acoustic Sensing (DAS) in an urban, shallow geothermal setting. Another major scientific question is to understand the fluid flow pathways and subsurface properties of the geothermal systems and potential changes as heat is extracted over time, which requires a baseline or initial state measurement of the mine before water is circulated.
In January 2022, we visited the UKGEOS Glasgow site to conduct a cross-well seismic borehole survey using DAS and hydrophone arrays prior to the heat pump installation. Here, we assess the applicability of DAS as a monitoring technique in a noisy, urban, shallow geothermal setting through noise analysis and comparison to the hydrophone array. We find that while the DAS noise levels are higher and more likely to mask the source signal, DAS provides significantly higher spatial resolution compared to the hydrophone array and contains more information in the coda. Finally, we use cross-hole traveltime tomography to obtain a velocity profile between the two wells as a baseline measurement, which can after a repeated survey in the future be used to assess the subsurface effects of the water circulation over time.

Session: Seismology for the Energy Transition [Poster]

Type: Poster

Date: 4/18/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Joanna M. Holmgren

Student Presenter: No

Invited Presentation: 

Authors