Drilling Amadeo's boreholes for the installation of the geothermal probes

23 June 2008 - Comments (0)

Construction

The armed concrete slab being sturdy enough to stand any truck, it was time to bring in the drilling rig for working on the geothermal ground loops. We are going to drill 5 boreholes, at a depth around 93 meters, in which we will install the probes. All probes will be connected to a central point to form one big vertical loop.

Preparation of the drilling

The drilling rig, mounted on a truck, arrived on Amadeo's land Sunday morning. We work with GEOID, a company with hands-on experience on geothermal drilling.

We had prepared a small ramp to easily access the left part, from the armed concrete slab.

Digging the mud pit

We started digging a mud pit that is needed to provide water and receive the extracted material from the boreholes. It's about 2,5 meters deep. The mud pit will do for 2 boreholes. A new mud pit while be dug later for the other boreholes.

At that depth, we start to find clay that is easy to recognize with its grey color. The soil in this area is supposed to have little or no rocks (although we did find a layer of rock on the first borehole).

The mud pit is filled with water. A pump takes that muddy water and injects it under pressure in the borehole being drilled. The pressure brings up the material that is going back to the mud pit as we will see.

Raising the derrick

The derrick holds the drill pipes on which is fastened the drill bit. The first step is to deploy the derrick from the truck.

Installing the first drill pipe and the drill bit

The borehole is 146mm in diameter and is drilled with a rotating tungsten-carbide drill bit. This drilling technic is called hydraulic-rotary drilling.

The tungsten-carbide drill bits.

The drill pipes.

The second step is to pull the first drill pipe and to install the drill bit. Each drill pipe is 6 meters long.

Pulling the first drill pipe.

Installing the drill bit.

Starting to drill

Everything was ready to start. Muddy water is pumped into the hollow drill pipes, down to the drill bit. This cools and lubricates the drill bit. Under pressure, the mud travels back to the surface around the outside of the drill pipe, and goes back to the mud pit through a small surface channel.

Progression is slow. We count 3-5 days per borehole. As the drilling progresses, the muddy water leaves way to a mix of water and clay. By the end of the first day, the pool was all grey already.