How does the geothermal drilling site selection process work?

Before a drilling rig can be brought on site to start making a geothermal borehole, a whole bunch of planning needs to take place. A big part of this consists of working out where the borehole site itself needs to be situated, and there are a number of important steps to this process. 

Below, we provide a general outline of the key areas involved, from why this selection process matters to how it can influence planning. 

Why does it matter?

The site of a geothermal borehole can have a big impact on a range of factors. These include the kind of drill that will be needed to make the borehole, the depth of the borehole, the number of boreholes that will need to be drilled, and certain restrictions that might apply to the project. 

Understanding all of these variables is a critical first step. Poorly designed sites can end up being a massive waste of money, either due to immediate dysfunctionality or unexpected problems that emerge as time goes by.

The selection process

There are a number of steps involved in site selection and assessment.

Step 1: General geological survey

The first step will consist of a more desk-based approach. This will include looking at preexisting geological maps, regional heat flow data, and any other information on the site in question. 

These maps will be used to assess rock and soil types and determine thermal conductivity levels. They can also be used to assess potential complications, such as the presence of natural aquifers or old mines.

Step 2: Site assessment

Next, an in-person site assessment can be conducted. This might include checking how much space there is, access routes for drilling rigs, and site proximity to any other utilities. Based on these variables, the next logistical steps of the process can be outlined, with a rig being brought to the site to potentially drill test boreholes.

Step 3: Thermal Response Test

Next, a Thermal Response Test (or TRT) will need to be completed. These are done by circulating fluid through a test borehole for a couple of days, while collecting data to measure the thermal conductivity of the area. 

Final planning & drilling

Once all the relevant site data has been collected, the final borehole requirements should be known, and the actual boreholes can be drilled. 

Based on the thermal conductivity of the ground and the heating requirements of the property in question, the number of boreholes and their respective depths can be decided. They can then be drilled, the loops can be installed, and the whole thing can be hooked up to the heat pumps and set up. 

Having thorough assessments carried out to determine an appropriate borehole location is of critical importance, and it absolutely isn’t something that you can afford to skip out on. Reputable borehole drilling services will consider it an absolutely essential first step, and will often provide engineers to conduct the assessments for you as part of a turnkey solution.