The pioneering Eden Geothermal energy project is now more than halfway towards its target depth of 4.5 kilometres. 

Drilling into the granite at the home of the world-famous Biomes near St Austell in Cornwall began in mid-May this year and is making great progress. 

The midway mark of 2.25 kilometres has been successfully surpassed and with drilling continuing at around 70 metres a day, Eden Geothermal Ltd is optimistic that the target depth will be hit in the next two-and-a-half months. 

The company has also been greatly encouraged by the temperatures being recorded as drilling goes deeper and due to the ‘high heat producing’ granite and underlaying, they are confident that when 4.5 kilometres is reached the heat will be in the range of 170-190 degrees. 

When drilling of the first well is complete a downhole coaxial heat exchanger will be inserted. Water is injected into the well which is superheated as it is meets the layers of granite below.  

The hot water will then be pumped back up to the surface.  This heat will initially warm Eden’s Rainforest and Mediterranean Biomes, offices, kitchens and greenhouses. The same water will then be re-circulated to be superheated and used again. 

Scientists working on the project can check the subterranean heat and the geology at different depths by analysing the cooling fluid which is circulated down the well during drilling.  

Eden Geothermal Project Manager Max Skerratt said: 
“Going past the halfway point towards the Earth’s crust is a monumental moment for the project, like sailing over the Equator for the first time. The further down we go, the more we are discovering about what lies deep beneath our feet.  

“We know that it is very hot down there. The heat of the mud coming back up is telling us that.  We know that we can predict specific temperatures at specific depths, which is super encouraging as we head towards the completion of drilling of the first well.” 

Wellsite geologists from Cornwall-based GeoScience Ltd are sampling mineralogy throughout the project to help build on knowledge of the deep geothermal resource. It is hoped this will provide greater understanding of the geology at depth, enabling more resources in the region to become characterised as reserves. 

Following a successful first phase at Eden, the next is to drill a second well close to the first to a similar depth of around 4.5 kilometres.  

The project

The Project will drill and test the first 4,500-metre-deep well of a geothermal energy demonstration system at the Eden Project, followed by one year of heat production to demonstrate greenhouse gas (GHG) savings. It will build 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. 

The Project will include a one-year period of heat production from the single deep well, using a ‘co-axial’ circulation system.  The hot water produced will be used to provide direct heat to existing facilities at Eden and to new greenhouses due to be constructed on site within the next two years. 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.

KeyFacts Energy Industry Directory: EGS Energy