Eden geothermal project progressing on drilling first well

Drilling rig at Eden Project, Cornwall (source: screenshot, YouTube/

Alexander Richter 2 Sep 2021

The geothermal project at the Eden project in Cornwall, UK is making continued progress on drilling its first well as you can follow on the company’s twitter feed.

The company has now drilled to a depth of 3,755 meters and plans to “tripping out of the hole at 4,000 meters to run and cement casing, before embarking on the final section of the well.” On its website, the project describes in details the drilling plan.

For its first well the plan is to drill to a depth of 4,500 metres with plans to use that well then for heat supply for the Eden project.

Our first well is called EG-1 and is being drilled in sections.

Here the description on the drilling plan:

The conductor section was drilled before the main rig arrived, as part of the site completion. It’s a larger (34” – 36”) hole, which was drilled through the looser, weathered ground near the surface, until we reached competent bedrock, at 32m. Wide diameter steel conductor pipe was then cemented into place, to seal off the start of the well from any looser, softer ground and to form a stable start collar or ‘foundation’ for drilling.

The first section to be drilled by the main rig was the 26” section, between 32m and 240m. We used two 26” drill bits, weighing 630kg each to get to 240m. (The granite at Eden is extremely hard, so after a certain number of rotations, the bits become worn and must be replaced.) Then the drillstring was ‘tripped out’ (pulled out) of the well and this section was lined with 20” steel casing, which was subsequently cemented into place using specialist cement.

Next, the 17 1/2” section was drilled, using eight 17 1/2” bits. When this section was completed, at 1510m, the process of ‘tripping out’ of the well and ‘running’ and cementing casing  – this time 13 ?” diameter – was repeated.

We are now drilling the longest section of the well – the 12 ¼” section, using a 12 1/4” drill bit. At 1,706m we “kicked off”: that is, the well started to be drilled directionally, deviating east away from the vertical and towards the target zone in the Great Crosscourse fault. Now that we’re drilling directionally, the measured depth (MD) of the well – its total length from start to end – starts to become greater than its total vertical depth (TVD) – the vertical distance from the well surface to the deepest point.

The 12 1/4” well section will be cased at around 4000m MD.  After this point, we will use an 8 1/2” drill bit to drill the 8 1/2” diameter section, which is designed to be open-hole (or perhaps lined with a perforated liner).

Picture:  Eden Geothermal Wellbore diagram (source: Eden Geothermal)

Source: Eden Geothermal