Igne was awarded the contract to drill a new borehole for the football club. The borehole was drilled to a depth of some 135m into the underlying chalk aquifer. Up to 14,000 litres per hour has subsequently been abstracted for the irrigation of Reading's pitches.

The borehole was drilled at a diameter of 790mm to a depth of 6m, and a length of 500mm diameter steel casing was then lowered into the borehole. The annulus surrounding the casing was filled with cement grout from the base of the borehole back to surface and allowed to cure for a period of 24 hours.

This so-called starter casing provides a stable, near-surface, safe working platform for the drilling rig and helps prevent any surface blow out.

Rotary drilling then continued at a diameter of 460mm down through the London Clay and the Thanet Sands into the top 3-4m of the underlying chalk at a depth of approximately 90m below ground level (BGL).

These ground conditions are particularly challenging, and Reading FC knew they needed a drilling contractor with extensive complex ground condition experience.

Considerate contractors with complex ground condition experience

A 90m long string of 273mm OD x 6m long carbon steel casing was welded together and lowered to the base of the borehole. The annulus surrounding the casing was then pressure grouted with approximately 10 tonnes of OPC grout from 90m back to the surface.

A further period of curing then took place to allow the grout to fully set and harden before continuing rotary drilling to approximately 135m BGL at 250mm diameter.

All drilling returns were cleaned via a system of hydro-cyclones and a shale shakers to remove the solids and allow the re-cycling of the drilling fluid back through the drill string, thus repeating the process until completion. This had the added benefit of keeping the site immaculately clean for our client.

As the unstable London Clay and Thanet Sands were sealed off and supported by the 273mm carbon steel casing, we determined the chalk was sufficiently competent to stand as an open hole construction.

Should unstable conditions ever be found within a chalk sequence, a secondary uPVC casing and screen can be utilised to prevent any spalling of the chalk and to provide a safe passage for a submersible pump.

Upon completion of the drilling programme for Reading FC, the borehole was developed via an eductor airlift to remove any residue of drilling fluids and to open the fissures to allow the full potential of the borehole to be exploited.

If further development had been required, a dilute solution of 30% hydrochloric acid would have been introduced to open the fissures. The acid is neutralised by the chalk and thus rendered safe - however, in this case it was unnecessary.

Once completed the borehole was test pumped to the satisfaction of the Environment Agency to prove sustainability and that there was no derogation of any other users within close proximity. The borehole was equipped with a submersible pump which discharged to a 690,000 litre holding tank that supplies water for the irrigation system.

Igne

With over 70 years' experience, we at Igne are your borehole experts. Whether you want to abstract water for irrigation or to generate geothermal energy to heat or cool, we have the in-house expertise and equipment to support even the most complex or ambitious project.

Our clients include the UK's water utilities companies, the NHS, the world's largest drinks manufacturers and hopefully you!

Client Testimonial

We had the pleasure of working with WB + AD Igne’s on a challenging development in London. The team, led by Richard, presented themselves as a well organised and extremely professional drilling company. We’ve absolutely no doubt that this will be the one of many successful projects together."

Contact us to discuss how we can support your project today. 

Photo Credits: McArdle Sport Tec