Hydrothermal systems in deep carbonate bedrock are among the most promising low-enthalpy geothermal plays across Europe. Apart from a few areas where viability of hydrothermal heat and power generation has been proved, most deep carbonate bedrock has received relatively little attention, because such rocks are perceived as ‘tight’. Exploration and development of the deep subsurface is an acknowledged high-risk investment, particularly in low-enthalpy systems, where tapping suitable temperatures for geothermal energy commonly requires drilling to depths of more than 3 km. In order to de-risk these challenging geothermal plays, it is crucial to improve our understanding of geological conditions that determine the distribution and technical recoverability of their potential resources. The efficacy of carbonate bedrock geothermal plays is crucially dependent on groundwater yield controlled by fracture conduits and karstification. This project identified the generic structural controls in deep carbonate formations, through a comparison of geological situations and their structural inventory, as well as collation of deep borehole data and their petro- and hydro-physical characteristics. A consistent assessment and the sharing of knowledge – bringing all partners to a common high level – resulted in uniformly applicable best practice workflows for estimation, comparison and prospect-ranking of hydrothermal resources in deep carbonate bedrock. Applied in eleven target areas by means of 2D or 3D mapping and characterization, these spatial assessments helped in de-risking the setup or maturation of regional plays, reveal possible cross-domain implications, and support sustainable subsurface management.

Dissemination and accessibility of Hotlime’s results

HotLime’s results of mapping and characterization, estimation, comparison and prospect ranking of hydrothermal resources in deep carbonate are provided in two principal synopses:
The results of mapping and characterization of the geothermal reservoirs after finalizing WP2 by the end of 2019, are summarized and compared in the HotLime Midterm Summary Report.
Based on these findings, play and prospect evaluation (WP3) has been implemented and deep carbonate play development strategies and impact (WP4) have been deduced, summarized in map sets on each of the eleven HotLime Case Study areas and supplemented by the hyperlinked knowledge base featuring cross-sections, reports, factsheets and the comprehensive LOD concepts vocabulary, the HotLime Geothermal Atlas.

Direct access to HotLime’s public deliverables:
D2.0 Summary report of resources mapping and characterization
D3.1 Report on play and prospect evaluation
D4.1 Report on deep carbonate play development strategies and impact
D5.1.1 HotLime partners’ legislation synopsis

Project facts:

Project duration: 1 July 2018 – 30 June 2021.
Project Lead: Timo Spörlein, Bayerisches Landesamt für Umwelt.
Project page on GeoERA website: https://geoera.eu/projects/hotlime6/

All maps presented in the HotLime Geothermal Atlas and more spatial representations of the geothermal base assessment are also available as georeferenced, queryable, combinable and downloadable map layers, retrievable via the EGDI Metadata Catalogue, and visualized in the GIS viewer for Hotlime results:

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