Map showing licences granted for Dogger aquifer operations.
About forty geothermal plants are now in operation in the Paris region, supplying hot water and heat from the Dogger aquifer to some 210 000 housing units.
The Dogger aquifer has been supplying hot water for district heating networks since the 1970s. It is a very productive aquifer, with water extracted at a temperature of 55° to 85° from depths of 1500 to 2000 metres. But over time, the performance of some wells has been affected by corrosion and deposits, and by drops in productivity or cooling due to "cold bubbles" forming around the reinjection wells.
A scientific and technical monitoring programme has now been implemented by the ADEME and BRGM to improve the management of existing plants and develop the aquifer's considerable unexploited potential. This is crucial to meet the requirements of the "Grenelle" policy on revitalising district heating networks, with production to be trebled by 2020.
Lowering a pressure-temperature sensor to the bottom of a Dogger well.
Recording the history of the Dogger
The purpose of the database is to improve our understanding of the aquifer and how it is likely to evolve, to ensure that the reservoir and extraction are monitored over the long term and to support the development of technical solutions to resolve operational problems.
The database was launched by the ADEME and the BRGM in 2001 to compile all available geological, hydrodynamic, thermal and geochemical data on the resource and the characteristics of the geothermal plants extracting the hot fluid, as well as their operational monitoring data. It is now available online for operator access to all relevant data on the geothermal plants (location, tubing, depth, etc.), on the aquifer itself (transmissivity, temperature, water layer thickness, productivity, etc.) and on plant operations (geochemical data, pressure, flow rates, temperatures, corrosion and anti-corrosion treatments, etc.), as well as historical data (commissioning dates, operational status, maintenance, etc).
In 2016, the BRGM considerably improved coverage by incorporating data on all the operations conducted by some thirty geothermal plants from 2013 to 2015.
The database in fact provides a record of the history of Dogger operations since the 1980s, thanks to the continuous input of production data from plant operators and of all the information from the periodical monitoring conducted by specialised engineering consultancies.
The database can be used directly by operators and has become an essential source of information for the subsoil engineering consultancies responsible for the pre-project investigations required to apply for exploration licences and permission to commence work, both for new operations and for the rehabilitation of older plants.
Geothermal engineers, especially those working for administrative bodies responsible for processing applications, but also for industry, have applauded the initiative and would like to see the database extended to all existing operations in France and to all aquifers liable to become targets for geothermal energy prospecting.
An extract from the "Dogger" database.