Low Temperature Deep Geothermal Operations for Direct Use in France: development of a national geothermal database and last review

International audienceAs part of a better monitoring of low temperature (30-150 °C) deep geothermal operations for heat production in France and in order to promote this form of renewable energy throughout the national territory, BRGM (French Geological Survey) in collaboration with ADEME (French Environment and Energy Management Agency) have implemented an application (web-based geothermal database) to follow-up detailed information on geothermal operations. Initially the database was defined to collect and disseminate geothermal data of the "Dogger" aquifer exploitations of the Paris basin, first sustainable aquifer used for district heating in France. Since 2018, the database has been extended to all deep geothermal operations in France for direct use (i.e. Paris basin, Aquitaine basin, Rhine Graben, South East basin, Limagne) and counts about 220 geothermal wells with 135 wells still operating. The objective of this "national" database is to provide valuable information to project developers who need accurate data during feasibility studies and regulation and permitting processes. It also targets local authorities and private or public stakeholders to provide them information about current operations, resources and potential applications for heating. Moreover, the system is also promoting the use of geothermal energy as part of the objectives of the law on Energy Transition and Green Growth, which sets a target of 38% of renewable energy sources in final heat consumption by 2030 in France. The article gives also a review of low temperature geothermal operations in France. 1. INTRODUCTION In order to identify and monitor deep geothermal exploitations for low temperature heat production (temperature range between 30-150°C) in France, BRGM and ADEME have developed a geothermal database in the early 2000's. Initially this geothermal database included well and reservoir characteristics (location, deviation, casing information, depth, hydrodynamic parameters…) and well monitoring data (pressure, temperature, flowrate, chemistry) of the Dogger limestone aquifer in Paris basin which is the main targeted aquifer for district heating networks in France since the early 1970's. Since 2007, with the successful recovery of geothermal activity, and after 20 years of no new geothermal operations, 60 deep geothermal wells were drilled in the Paris basin in Ile-de-France region for the supply of district heating networks. Other operations are in progress or have been carried out in the Rhine Graben for heat production or cogeneration (heat and electricity) due to higher temperatures and also in the Aquitaine basin (second sedimentary basin in France harnessed for geothermal energy) in Nouvelle-Aquitaine region with the implementation of a first deep geothermal operation (doublet) targeting the Jurassic limestone in summer 2019