Original paper
Karstified and fractured Lower Carboniferous (Mississippian) limestones of the UK ‒ A cryptic geothermal reservoir
Narayan, Nadia S.; Adams, Charlotte A.; Gluyas, Jon G.
Zeitschrift der Deutschen Gesellschaft für Geowissenschaften Band 172 Heft 3 (2021), p. 251 - 265
45 references
published: Dec 27, 2021
published online: Jul 1, 2021
manuscript accepted: May 28, 2021
final revised version received: May 11, 2021
manuscript revision requested: Apr 14, 2021
manuscript received: Mar 17, 2021
Open Access (paper may be downloaded free of charge)
Abstract
Karstified and fractured Lower Carboniferous (Mississippian) limestones of the UK have been evaluated for their geothermal potential. This wholly undeveloped resource is calculated to be in excess of 26 million GWh (95 EJ) for the P90 case and as much as 35 million GWh (129 EJ) for the P50 case for six regions in England and Wales, ranging in scale from Kent at 0.04 million GWh (P50) to Northern England at 15 million GWh (P50). The evaluation used three sources of evidence to assess the distribution, current burial depth, likely temperatures and transmissivity of these limestones. Seismic and outcrop data, well logs and cores from drilled wells and water chemistry data from thermal springs were used to demonstrate the presence of deep, water bearing, permeable limestones. Geothermometry calculations using spring-water composition data provided clues about temperatures at which the issuing water equilibrated with its original host rock indicating that water now reaching the surface had acquired its solutes at temperatures significantly in excess of 30 °C and depths much greater than 1 km. The UK uses about 2.5 EJ per annum yielding a resource to use ratio of 40-50 years assuming no natural inflow or reinjection of cooled water for reheating.
Keywords
geothermal energy • karst • Mississippian carbonates • fractured reservoir