Geothermal district heating in Cachan
Overview
In the suburban town of Cachan, near Paris, a geothermal district heating has been implemented and expanded to provide hurban heating to the area.
The project's success in Cachan, managed by a DALKIA/City of Cachan joint venture, marks a significant advancement in geothermal technology, opening new possibilities for geothermal development in densely populated areas with moderate reservoir performance. As a testament to this innovative approach, the second subhorizontal well was successfully completed and tested, further proving the efficacy and potential of subhorizontal geothermal well architecture.
This geothermal plant meets the heating and hot water needs of over 7,000 housing equivalents, including public facilities, apartment buildings, and businesses.
Technical details
On December 13th, 2017, the first subhorizontal geothermal well, designed and supervised by GPC IP, was completed for DALKIA (EDF Group). This well, a world premiere in geothermal engineering, features a 1,001-meter long, 87° slanted openhole drain in the Dogger/Bathonian oolithic limestone reservoir at a true vertical depth of 1,550 meters.
The innovative subhorizontal drilling technique, typically reserved for oil extraction, significantly enhances geothermal efficiency. This well, capable of a 450 m³/hr nominal discharge and a 16 MWth rated capacity, will be complemented by an injection well of similar design, forming a doublet that will replace two aging geothermal doublets from 34 years ago. The second doublet improved flow rates and heat production, providing at least 400 m³/hr of hot water, compared to 300 m³/hr from the old wells.
Investments
The construction, initiated in late September 2017, was completed in February 2018 with a total investment of €19 million, 30% of which was funded by ADEME and the Region's heat fund.
Summary
Depth: 1,550 meters
Units covered: +7,000 housing
Investments: €19 million