CHPM2030 DELIVERABLE D6.2.1. REPORT ON PILOTS: EVALUATION OF THE CHPM POTENTIAL OF CORNWALL, SOUTH WEST ENGLAND Summary: This report investigates the potential for combined heat and metal production from south-west England, considering availability of legacy geoscience information, the geological environment, geothermal characteristics, potential for deep metal enrichment, and technical, environmental, social and regulatory factors that could influence the future development of this technology in the region. Authors: Paul A J Lusty, British Geological Survey, Principal Economic Geologist Richard B Haslam, British Geological Survey, Structural Geologist Richard A Shaw, British Geological Survey, Economic Geologist Eimear A Deady, British Geological Survey, Minerals Geoscientist Paul Williamson, British Geological Survey, Senior Geophysicist This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement nº 654100. CHPM2030 DELIVERABLE 1.1 TABLE OF CONTENTS Table of contents .................................................................................................................................. 2 LIST OF FIGURES ................................................................................................................................... 3 LIST OF TABLES ..................................................................................................................................... 8 1 Executive summary ...................................................................................................................... 9 2 Introduction................................................................................................................................ 14 2.1 Objectives and role of the CHPM2030 project ................................................................... 14 2.2 UK CHPM2030 study area selection ................................................................................... 14 3 Geology of the prospective area ................................................................................................ 22 3.1 Regional geological history ................................................................................................. 22 3.2 Tectonic framework ........................................................................................................... 26 3.3 Geology of the CHPM2030 study area ............................................................................... 29 4 Geophysics of the prospective area ........................................................................................... 42 4.1 Previous work and data availability .................................................................................... 42 4.2 Tellus magnetics data reassessment .................................................................................. 50 5 Deep metal enrichment.............................................................................................................. 55 5.1 Types of mineralisation in the CHPM2030 study area ....................................................... 55 5.2 Controls on mineralisation ................................................................................................. 61 5.3 Potential for deep metal enrichment ................................................................................. 61 5.4 The batholith as a metal reservoir ...................................................................................... 62 5.5 Applicable leaching agents based on WP2 ......................................................................... 64 6 EGS potential .............................................................................................................................. 66 6.1 Geothermal characteristics of the area .............................................................................. 66 6.2 Evidence for deep fluids ..................................................................................................... 76 7 Integrated modelling .................................................................................................................. 79 7.1 Regional model ................................................................................................................... 79 7.2 Hot dry rock project site model .......................................................................................... 89 7.3 United Downs Deep Geothermal Power project site model .............................................. 91 7.4 Uncertainties and limitations ............................................................................................. 93 8 Information for CHPM technology development ....................................................................... 97 8.1 Underground heat exchanger and metal enrichment ........................................................ 97 8.2 Production and injection wells ......................................................................................... 102 8.3 Power plant and local energy demand ............................................................................. 104 8.4 Salt gradient power generation ........................................................................................ 104 9 Operational characteristics ...................................................................................................... 107 9.1 Environmental, social and political background ............................................................... 107 9.2 Financial aspects............................................................................................................... 119 10 References ................................................................................................................................ 121 Appendix 1 Borehole data used to determine the depth to granite surface. ............................. 134 Appendix 2 Extracts from the RH15 core log............................................................................... 140 Appendix 3 Properties simulated, interpolate or calculated through the model volume. .......... 143 Appendix 4 Fracture density statistics and histograms from calculated fracture density. .......... 147 Appendix 5 The parameters used for the three DFN models for the HDR site. Note the three density models used in the three models. ....................................................................................... 151 Page 2 / 158 CHPM2030 DELIVERABLE 1.1 Appendix 6 Calculated permeability in each of the principal grid orientations (i, j, k) and for each of the HDR model based on the corrected Oda method for fractures with a horizontal length greater than 150m. 152 Appendix 7 Calculated permeability in each of the principal grid orientations (i, j, k) and for each of the UD model based on the corrected Oda method for fractures with a horizontal length greater than 150m. 155 Appendix 8 Modelled permeabilaties for the UD model ............................................................. 156 LIST OF FIGURES Figure 1: The deep geothermal energy potential of Great Britain. A. Surface heat flow map. B. The locations of significant high-level heat producing granites. Reproduced, unmodified from Busby and Terrington (2017), under Creative Commons Attribution 4.0 International License (http://creativecommons.org/ licenses/by/4.0/). © The Author(s) 2017. ................ 15 Figure 2: Simplified geological map of south-west England showing the distribution of sedimentary basins and the location of the granites of the Cornubian Batholith. The sedimentary basins typically comprise undifferentiated siltstones, mudstones and sandstones, with subordinate conglomerate. Modified from Shail and Leveridge (2009) with additional BGS data. ............................................................................................................................................................................ 16 Figure 3: Rosemanowas Quarry, Cornwall, the Hot Dry Rock (HDR) project drilling site. A. Pump infrastructure used in the hydraulic stimulation experiments. B. Equipment used in the viscous fluid hydraulic stimulation experiments. Images reproduced from the HDR project photo archive held by the British Geological Survey. C. The quarry in 2017, which is used for testing geophysical equipment. D. The three HDR project borehole collars. E. Core from HDR project borehole RH12. F. Core from HDR project borehole RH15. British Geological Survey © UKRI. ........................................................................ 17 Figure 4: The Variscan belt in central and western Europe and major W-Sn and polymetallic minerals deposits. Reproduced, unmodified from Timón et al. (2019), under Creative Commons Attribution 4.0 International License (http://creativecommons.org/ licenses/by/4.0/). ............................................................................................................... 18 Figure 5: The Cornubian Orefield of south-west England. Modified from Dunham et al. (1978). ....................................... 18 Figure 6: Typical Cornish mineralisation and exposures of granite. A. The Crowns Engine house, Botallack, Cornwall, evidence of the long history of mining in the region. B. Greisen bordered sheeted tin-tungsten veins occur in granite at Cligga Head on the north coast of Cornwall. C. South Crofty Mine, Robinson's Section, 380 fm. level, No. 4 lode west. Cassiterite/tourmaline filled fractures forming No.