Borehole drilling: What is it?

How do we create a borehole?

There’re several different ways of borehole drilling, including rotary drilling, percussion drilling, and auger drilling. The most typical method for borehole drilling in the UK is using a rotary drill. Although an experienced driller will know which method is best depending on the UK area.

A rotary drilling rig bores a long narrow hole into the ground using a drill bit on the end of a drill pipe. This pipe rotates extremely quickly, somewhere between 50 and 120rpm. The driller will also use air or drilling fluids to flush out the borehole, reduce friction and cool the drill bit. This method of borehole drilling is very effective method of boring through both hard and soft rock. The borehole is then lined with a special casing that stops it collapsing in on itself.

That’s where it gets quite specialist depending on the geology of where we’re drilling in the UK. Some areas like London are notoriously tricky to drill. This is because of the combination of gravel, chalk and clay that’s found below ground.

Why haven’t I heard of borehole drilling before?

Good question, it’s common knowledge that the UK has been over reliant on fossil fuels for too long now. Gas boilers for heating our homes and water account for 85% of all UK heating systems.

Since 2010 to combat this there’s been lots of government investment in solar and wind power. But in the last few years heat pump technology is becoming more of an option in the UK. That’s where borehole drilling comes in. 

Of course, most people buy a house or run a business assuming their only option for water and heating is from a mains supplier. Rising energy and water costs, and more recently water supply issues means many people are asking if there are other alternatives. So yes there is, and borehole drilling is an excellent way to access those alternatives.

Different types of borehole drilling

Whilst there’ s several reasons to drill a borehole, there are two main types of borehole drilling we carry out:

Borehole drilling for heat pumps

Sometimes known as geothermal drilling, heat pump boreholes are around 190m deep (roughly 20 buses bumper to bumper). This might seem deep it’s here we can access the ground source heat that the sun’s rays generate. A ground source heat pump (GSHP) then helps get this heat into a building via an open or closed loop system.

Borehole drilling for a heat pump can seem like a more expensive option compared to horizontal trench systems. These are large shallow trenches that cover a large area of land. If you have a large plot of land, digging trenches can lower the initial cost of installing ground source heating, however it can take roughly a year for the ground to recover. Boreholes are just a much more practical solution. This is especially true if you live in an urban area with only a garden, driveway, or limited space.

Vertical borehole drilling also represents a more reliable energy source – trench systems are vulnerable to temperature changes, the depth of a geothermal borehole means it remains at a constant temperature.

Borehole drilling for Water

The process of borehole drilling for water, is much the same as for heat pumps, however it’s often not as deep. When we drill a borehole for water we drill down to the natural water that’s stored in the rock underground known as aquifer (around 60m). We will always drill to the aquifer rather than the water table, even though the borehole won’t need to be as deep. This is because the water stored in the aquifer is stable and isn’t subject to above ground fluctuations like droughts. We then install a pump that gets this water to the surface, and to your home or where ever you’d like it to go!

Where can we drill boreholes?

Borehole drilling can be done almost anywhere. We often drill on driveways or back gardens. We’ve adapted our drills for tight spaces, as long as the ground is strong enough to support our drill and there are no underground pipes or cables, we can usually go ahead.

In the UK, most property owners don’t need planning permission to have a water borehole and/or a geothermal borehole. For businesses and landowners who use over 20 cubic metres of water per day you may need a water abstraction license. It’s best to check with the Environment Agency.

In the case of water boreholes, we do need to know if there is water on your property. To do this we carry out checks with the British Geological Survey (BGS). We’ll find out about the type of geology in your area and if there are other water wells already drilled nearby. This also gives us an idea of the type of drilling techniques we need to use and the depth we need to drill. 

With GSI’s water well drilling service we offer a ‘no water, no charge’ guarantee, so you can be confident we won’t drill if we think there’s no chance of water on your property.