The Cachan geothermal project is revolutionizing sustainable energy with the world’s first subhorizontal trajectory wells. This groundbreaking initiative, set in the densely populated Paris Basin, is designed to enhance the efficiency and sustainability of urban heating systems by leveraging cutting-edge geothermal engineering techniques.
Project Goals
The primary objective is to validate the concept of subhorizontal well architecture. This innovative design bridges the gap between horizontal drains that exploit single reservoir levels and multilateral wells that target multiple levels. By optimizing the exploitation of stratified reservoirs like the Dogger in the Paris Basin, this project promises a 30% increase in productivity compared to conventional doublets.
Local Context
The project replaces two aging geothermal doublets, operational since 1984, with a single, high-performance doublet. Situated in a region with a high density of geothermal systems, the new well architecture addresses the challenges of limited transmissivity while meeting the growing energy demands of urban populations.
Key features of the project include:
- Exploiting the Bathonian section of the Dogger reservoir.
- Achieving a maximum flow rate of 450–500 m³/h, significantly higher than the 350 m³/h of the older doublets.
- Producing 60–65 GWhth annually, reducing reliance on fossil fuels.
Innovative Engineering
The subhorizontal well design is a testament to the integration of advanced oil and gas drilling technologies into geothermal engineering. Real-time geosteering, logging-while-drilling (LWD), and spectral analyses (XRF and XRD) ensured precise navigation through the stratified reservoir. This meticulous approach resulted in record-breaking drain spans of over 1,000 meters, optimizing reservoir exploitation.
Sustainability Impact
By replacing outdated systems with this innovative doublet, the project:
- Reduces CO₂ emissions by transitioning to renewable geothermal energy.
- Enhances energy efficiency with a coefficient of performance (COP) of up to 28.
- Lowers operational costs while increasing energy output.
Hydrothermal Modeling and Results
Forecast simulations demonstrate minimal environmental impact after 30 years of operation. The advanced well architecture ensures compatibility with the natural flow regime of the aquifer, maintaining long-term sustainability.
A Milestone in Geothermal Energy
The Cachan project is more than a technical achievement—it’s a blueprint for the future of sustainable urban heating. By combining modern drilling standards, interdisciplinary teamwork, and innovative engineering, it sets a new benchmark in geothermal energy.
This pioneering initiative underscores the role of renewable energy in combating climate change and advancing the global energy transition.