The Burbo Bank Job

Don’t panic, we haven’t been drilling into the Nat West vaults and making off with the swag, just another good honest day’s drilling - this time for the Burbo Bank Wind Farm.

This is an off shore project for Sea Scape Energy. The development will occupy a 10sq km area of seabed and includes 30 wind turbines located on The Great Burbo Sands Flats in Liverpool Bay. The turbines will be connected via 3 export cables, brought on shore at Wallasey on the Wirral Peninsula.


This is where we come in. Our part in the project was to bring the export cables on shore. This involved drilling 3 shots of 200 metres out under the concrete sea defences, each bore carrying 450mm HPPE SDR 11 ducts.

Not as easy as it sounds!

The biggest problem was probably the formation change from soft sands into compacted clays – all on the same shot

Drilling through sand brings its own problems. Correct drill heads and drilling speeds are essential to stop the sand compacting and avoid the drill or pipe getting stuck.

We have to keep the bore open and stop collapses. To do this the muds must be mixed to the correct consistency and there must be enough of them. All this whilst making sure the clays don’t swell.

This is where we come in to our own. Our Vermeer D80 drill rig is fitted with a 350 gallon per minute pump - setting us apart from most rigs of this size.

As an environmentally aware company we recycle our drilling fluids whenever possible. This is where the dreaded sand could come back and haunt us! If it gets into the drill rig’s mud pump its abrasive qualities (especially under pressure) could quickly cause terminal damage but our newly acquired SiteTec recycling unit coped admirably reducing the sand content of the recycled fluid from around 30% to under 1%.

On coastal jobs such as this one there were also the tides to be considered

We had to drill to tide times so the drill head was in the end of the bore at high tide to avoid the bore filling with water, as this could wash out the muds and cause a collapse. The timing of the tide was most important when pulling the pipe. We had to be sure the pipe was not caught by the tide as it could snap if lifted and kinked by the force of the water. Despite all these time restrictions we still finished the 3 shots a week ahead of schedule.

On completion, all three 450 ducts were checked using CCTV to prove their integrity before cables are installed. Once that’s done we’ll be back on site to seal and grout everything.