Rapid Grout Level Monitoring in UKGEOS Boreholes Using Downhole Electrical Measurements

The UK Geoenergy Observatories (UKGEOS) project aims to advance our understanding of subsurface energy resources. A rapid grout level monitoring method using electrical contact resistance was developed and deployed in geothermal boreholes. This technique enables efficient assessment of grout distribution during ground source heat (GSH) borehole installation, ensuring backfill integrity and preventing blockage. This study presents contact resistance profiles for one GSH borehole during grouting stage, showing a clear interface between grouted and non-grouted sections. The GeoTom ERT device facilitated rapid geo-electrical monitoring, allowing for accurate measurements and immediate corrective actions. The sensitivity of the method to resistivity variations from injected geothermal grout was observed. By switching between two electrode strings at different depths, grout levels were effectively and efficiently tracked, enabling successful backfilling of the borehole. This approach offers advantages of cost and time savings, improved grouting continuity, and enhanced operational efficiency. This application also demonstrates its potential for enhancing safety and reliability in geotechnical and geoenergy projects. Advanced monitoring methodologies are essential for effective decision-making and quality control in borehole construction. The findings contribute to the knowledge and advancement of grouting practices, emphasizing the importance of employing such techniques for successful project outcomes.