UK Low Enthalpy Geothermal Resources: the Cheshire Basin

Geothermal energy extraction from low enthalpy resources within the UK is something of a hot topic; whilst the UK has only one working geothermal system (Southampton), there is scope for geothermal energy to make a more significant contribution to the UK energy portfolio. A major assessment of UK geothermal resources was undertaken by the British Geological Survey, between 1976 and 1986. This identified low enthalpy resources associated with Permian and younger sedimentary basins. The total resource held within these basins was estimated at 292.6 EJ (Rollin et al., 1995); many times larger than the entire UK heating demand. More recently, work undertaken by Newcastle University and Durham University included drilling two new geothermal exploration wells at Science Central, Newcastle-Upon-Tyne and Eastgate, County Durham respectively. These wells both penetrate Carboniferous strata, and in the latter case the Devonian Weardale Granite. No wells have been drilled to further assess the potential held within Mesozoic basins. One of the prospective areas for development of geothermal energy is the Cheshire Basin. A recent Deep Geothermal Review Study of the UK (Atkins, 2013) highlighted the basin as being a probable heat generating reserve. It comprises Permo-Triassic sediments extending to at least 4.5km depth, underlain for the most part by Carboniferous strata. Temperatures are estimated to reach 100°C at 4.5km. The underlying Carboniferous Coal Measures and Namurian shales are gas and oil prone respectively and in the linked East Irish Sea Basin to the north-west have sourced the petroleum deposits found in both Morecambe Bay and Liverpool Bay. Shows of petroleum are common in the Cheshire Basin but only two sub-commercial deposits have been found. We also know from many wells in the East Irish Sea Basin that the strata are permeable, capable of flowing at rates of at least 10 liters sec -1 ; a figure comparable with that achieved by the UK’s single low enthalpy geothermal scheme in Southampton. The Cheshire Permo-Triassic rocks are also excellent aquifers and have been exploited extensively, particularly in the Peckforton Hills. The combination of permeable formations at temperatures of around 100oC at 4.5km coupled with the possibility of producing associated hydrocarbons (which could be an additional high-value energy stream) could provide a viable new domestic energy resource. The Cheshire Basin also lies close to the large population centres of Manchester and Liverpool both of which could benefit substantially from low carbon, district heating schemes.