A deep geothermal exploration well at Eastgate, Weardale, UK; a novel exploration concept for low-enthalpy resources

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doi: 10.1144/0016-76492006-015
Authors:Manning, David A. C.; Younger, P. L.; Smith, F. W.; Jones, J. M.; Dufton, D. J.; Diskin, S.
Author Affiliations:Primary:
Newcastle University, School of Civil Engineering and Geosciences, Newcastle upon Tyne, United Kingdom
Other:
FWS Consultants, United Kingdom
PB Power, United Kingdom
Foraco-Boniface SA, France
Volume Title:Journal of the Geological Society of London
Source:Journal of the Geological Society of London, 164(2), p.371-382. Publisher: Geological Society of London, London, United Kingdom. ISSN: 0016-7649
Publication Date:2007
Note:In English. 31 refs.; illus., incl. anals., 7 tables, strat. col.
Summary:The first deep geothermal exploration borehole (995 m) to be drilled in the UK for over 20 years was completed at Eastgate (Weardale, Co. Durham) in December 2004. It penetrated 4 m of sandy till (Quaternary), 267.5 m of Lower Carboniferous strata (including the Whin Sill), and 723.5 m of the Weardale Granite (Devonian), with vein mineralization occurring to 913 m. Unlike previous geothermal investigations of UK radiothermal granites that focused on the hot dry rock concept, the Eastgate Borehole was designed to intercept deep fracture-hosted brines associated with the major, geologically ancient, hydrothermal vein systems. Abundant brine (≤46°C) was encountered within natural fracture networks of very high permeability (transmissivity c. 2000 darcy m) within granite. Evidence for the thermal history of the Carboniferous rocks from phytoclast reflectance measurements shows very high values (≥3.3%) indicating maximum temperatures of 130°C prior to intrusion of the Whin Sill. Geochemical analysis of cuttings samples from the Eastgate Borehole suggests radiothermal heat production rates for unaltered Weardale Granite averaging 4.1 µW m-3, with a mean geothermal gradient of 38°C km-1. The Eastgate Borehole has significant exploitation potential for direct heat uses; it demonstrates the potential for seeking hydrothermal vein systems within radiothermal granites as targets for geothermal resources.
Subjects:Alkalinity; Boreholes; Brines; Carboniferous; Chemical composition; Electrical conductivity; Enthalpy; Geochemistry; Geothermal energy; Geothermal exploration; Geothermal wells; Granites; Hydrochemistry; Igneous rocks; Isotopes; Naturally fractured reservoirs; Paleozoic; Permeability; PH; Plutonic rocks; Radioactive isotopes; Temperature; Thermal properties; Transmissivity; Vitrinite reflectance; Durham England; England; Europe; Great Britain; United Kingdom; Western Europe; Eastgate England; Weardale England; Weardale Granite
Coordinates:N543000 N545700 W0011500 W0022200
Abstract Numbers:07M/1088
Record ID:2007026570
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States, Reference includes data from The Geological Society, London
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