Enough heat for a whole rainforest
Phase One of the Eden Geothermal Project, which is underway, is an industrial research project co-funded by the European Union through the European Regional Development Fund, Cornwall Council and Gravis Capital Management. We are drilling and testing the first 4,500-metre-deep well of a geothermal energy demonstration system at the Eden Project. This will be followed by one year of heat production to demonstrate greenhouse gas (GHG) savings.
The project is building on knowledge of the deep geothermal resource in Cornwall by providing greater understanding of the geology at depth, enabling resources in the region to become characterised as reserves.
When development of the first well, EG-1, is complete, there will be a one-year period of heat production from this single deep well, using a ‘co-axial’ circulation system. The hot water produced will be used to provide direct heat to the facilities at Eden. The use of this heat will demonstrate the benefits of greenhouse gas (GHG) savings achievable from this specific project, while also indicating the long-term level of GHG savings that could be achieved from a two-well system.
It is hoped that this will provide a pivotal first step for creating a new renewable and industry sector for the county and for the UK, as the greater understanding of the conditions deep in the granite will enable the subsequent development of another 4,500-metre well (EG-2) and a combined heat and power plant.
Eden Geothermal phase one: research project
Eden Geothermal phase two: EG-2 and electricity generation
The main stages of phase one of the Eden Geothermal Project are:
- Preparation and finalisation of design and procurement of specialist services;
- Site works;
- Drilling, completion and testing of the first deep well;
- Deployment of the co-axial system along with the installation of a heat main to Eden;
- Heat production and greenhouse gas savings from the first well for 12 months.
The finalisation of the site and well design, recruitment and the procurement of the main services required for the Project. This stage is now complete.
The enabling works required to prepare the site for drilling were undertaken by a specialist contractor. This work included: ground levelling; erection of a perimeter fence; creation of site access; construction of roadways, drill pad, wellhead cellars and lagoons; site drainage and flood alleviation; erection of site buildings; installation of seismic monitoring network; installation of services and conductor pipe. A dedicated public viewing area was also created.
Starting in May 2021, the first deep well (EG-1) will be a deviated well drilled to a vertical depth of approximately 4,500 metres using conventional rotary drilling with muds. The upper three sections will be lined with steel casing, but the bottom section will be left as an open hole.
The well testing programme will provide essential information on the hydrogeological characteristics of the target rock zone. Designed by the team in conjunction with University of Exeter, it will respond to the conditions encountered during drilling, with the aim of maximising the level of understanding of the petrography, hydrogeology and geomechanical conditions of the rock at 4,500m. The principal technical aims will be to:
- characterise the permeability/impedance of the target zone;
- evaluate the spatial extent of fracture distribution and orientation in the target zone;
- characterise the flowing zones and evaluate the ‘far-field flow contribution’;
- use acquired data to generate models to understand the regional geothermal resource.
The information obtained from the drilling and testing of the deep well will enable us to understand the characteristics of the target zone and the viability of the proposed development of the full-scale geothermal CHP plant at Eden.
Production, EG-2 and beyond
The final step in this first phase of the project will be to install a heat main from the geothermal site to the Eden Energy Centre and to provide geothermal heat from the well for the facilities at Eden. This will necessitate sealing off the well within the base of the production casing at a depth of ~3,500m and deploying open-ended tubing inside the well.
Water will be injected down the outer ring and will warm as it gains heat from the surrounding rock on its descent. It will return to surface via the centre tubing as hot water. The hot water will be circulated along the heat main to the Eden Energy Centre and then returned to the well and re-injected. The final Project report will set out the greenhouse gas savings achieved during this period.
Once installed, the heat production system will be operated for one year, supplying heat to Eden and demonstrating greenhouse gas savings. However, this period is likely to be extended beyond the duration of the Project during the drilling of the second deep well and the ensuing development of the system, until the CHP plant is brought on-line. The CHP plant will continue to supply heat to Eden using the heat main, and will also produce power.
Header image ©Hufton+Crow