GSHP borehole in running sands presents a challenge
Geologic Boreholes were contracted to drill 3 boreholes to provide heat collection to a ground source heat pump. The project was far from simple. The geology presented the first problem as GSHP borehole drilling in running sands can result in the GSHP borehole filling with silt when the borehole is uncased. With running sands across the site, each borehole required around 50M to be drilled using temporary casing. After extensive research about the site using data held within the office regarding geology, we decided to use a shell & auger rig to advance the casing through the sands. This decision was taken to limit the impact on the garden area and as a standard rotary rig would struggle to advance the casing through this complex geology. Once the casing was installed through the running sands, the geology would change to hard packed mudstone that would require a rotary rig to progress the borehole.
Access to the site prevented us simply towing the rig into the site and positioning it. Tne proximity of electricity lines around the site prevented us from using a standard crane to lift the rigs into position. As a result we called in the services of the largest demountable lorry mounted crane in the country which was parked in the driveway and then lifted the rigs into position. The 1.6Tonne rig was lifted over 15M horizontally and 11M vertically and was at the limit of the hiab’s performance.
Getting the GSHP borehole drilling rig in place
Test lifts were undertaken to ensure the lift was possible. It was such an unusual sight there were significant onlookers, at one point a passing police car even stopped to have a look at what was going on!!
Once in position the shell & auger rig installed the casing through the sands and the GSHP borehole drilling began. The rotary rig drilled to depth and the loops were installed.
Another successful GSHP borehole installation
The loops were installed and grouted as the casing was removed from the boreholes. The rigs were then lifted back out of the site. The heat pump is now connected and commissioned and the client is enjoying using the heating system without paying for heating oil.