Hydrogeothermal studies in the United Kingdom

Abstract

Following the increase in oil prices in the mid‐1970s, Britain assessed its geothermal resources. Low‐temperature, hot‐water resources, in the range 40°C to 100°C, occur in Permo‐Triassic sandstones in several deep sedimentary basins. In total these resources are estimated at 69.1 × 10 18 joules (J) (2576 million tonnes coal equivalent). Resources also occur in Upper Palaeozoic aquifers but, as the permeability of these aquifers depends upon fissures, exploitation is difficult. The only surface manifestations of hot water at depth are the warm springs at Bath and Bristol and in the Peak District and Taff Valley, which issue from the Carboniferous Limestone. The potential of radiothermal granites for Hot Dry Rock (HDR) development has also been investigated, particularly in the Carnmenellis granite in Cornwall. Three boreholes drilled in the granite to depths of over 2 km have been connected by developing natural fractures. Water circulation between the boreholes and through the fractured rock has been successful.

The measured shallow temperature field in Britain

“…Previous publications of the temperature field in Britain have concentrated on temperatures in the depth range of 4 -7 km (Downing and Gray, 1986a, b;Barker et al, 2000) since the purpose of those studies was to identify temperatures that might be suitable for geothermal electricity generation. In the past two decades it has become clear that the shallower heat, in the depth range above 1000 m, is a substantial and more easily accessible heat resource.…”

The Cornubian geothermal province: heat production and flow in SW England: estimates from boreholes and airborne gamma-ray measurements

“…The principal modifications to the UK mean heat flow of 55 mW m −2 are found in association with radiogenic granite intrusions. Barker et al (2000) note that the mean heat flow in the Cornubian granites of SW England is 117 ± 8 mW m −2 compared with maximum values of 101 and 76 mW m −2…”

“…The only deep temperature measurements were in the HDR boreholes at Rosemanowas quarry. Barker et al (2000) report temperatures of 79 °C at 2.1 km depth in well RH 12 and 100 °C at 2.6 km depth in well RH 15. The revised heat flow for the average of Rosemanowas A and D is 116.8 mW m −2 , which, with the constant heat production with depth model, gives subsurface temperatures of 84.3 °C at 2.1 km depth and 102.0 °C at 2.6 km depth, slightly higher than the measured temperatures.…”

“…The potential of geothermal energy systems in the UK was subsequently reviewed by Downing and Gray (1986a, b) and later by Lee et al (1987) and Barker et al (2000). The reviews and studies discuss low enthalpy systems in Upper Palaeozoic aquifers and thermal springs together with Mesozoic basins.…”

A survey of the inorganic chemistry of bottled mineral waters from the British Isles

“…Radiocarbon and tritium dating has also been carried out of thermal groundwater (27.5ºC) from St Ann's Well, the source for Buxton Spring water in Derbyshire. This has established that the water has a mixed origin with a proportion containing low though detectable concentrations of tritium (Edmunds, 1971;Evans et al, 1979) and an old tritium-free component with non-radiogenic carbon, together yielding a bulk age of some 5000 years (Barker et al, 2000;Evans et al, 1979). The water discharges from fractures in the karstic Carboniferous Limestone aquifer and circulation depths as great as 1 km have been postulated for this spring source (Brassington, 2007).…”