Drilling and as-built borehole design report for the UK Geoenergy Observatory in Cheshire

This report details work undertaken during the main drilling phase of the UK Geoenergy Observatory in Cheshire, which is a unique, at-scale field laboratory for research and innovation in aquifer thermal energy storage, rock volume characterisation and the monitoring of subsurface processes.

The Observatory, which entered into operation in April 2024, comprises 21 vertical boreholes drilled to 100 m depth and permanent surface equipment for heating, cooling and groundwater flow control. Boreholes are equipped with a high-resolution array of electrical resistance tomography electrodes, hybrid fibre-optic distributed temperature and acoustic sensing (DTS & DAS) cables and multilevel groundwater monitoring to allow subsurface change to be observed in close to real time. Extensive rock volume characterisation was performed during Observatory construction including the scanning of 1,800 m of drill core, geophysical wireline logging, porewater profiling and hydraulic testing.

The Cheshire Observatory boreholes were drilled in two phases: an initial ground investigation borehole (TH0424) was drilled from the 8th to the 30th of November 2021 to provide data to inform the Observatory design. A further 20 boreholes were then drilled between 15th August 2022 and the 25th July 2023. Both phases of drilling were undertaken by Marriott Geotechnical Drilling.
The Geoenergy Observatories are operated by the British Geological Survey and are NERC/ UKRI facilities. They are available to the whole of the UK science community for research, innovation and training activities.

The drilling report and appendices include:
 Details of the drilling of each of the boreholes and well construction specifications.
 Details of each of the installations run and the material used.
 Borehole schematics.
 Details of the data collected during the drilling phase including wireline logs, core,
sub cores, fluid samples etc.
 Well instrumentation and sensor positions.
 Issues encountered and lessons learned.

The Cheshire site is located within Thornton Science Park (TSP), approximately 10 km north of Chester. It is well placed to support energy storage research by energy intensive industries in the Cheshire Science Corridor Enterprise Zone.