Horizontal Directional Drilling or directional boring is a method used to install underground pipelines in a shallow arc form through trenchless methods. It involves the use of a directional drilling machine and attachments that allow accurate drilling of the chosen bore path. Directional boring with these special machines installs underground water lines and geothermal lines without any impact to the surface area or disruption to traffic flow, landscaping, or structures.

 

Directional boring is the preferred method when trenching or excavation is not the most practical of the methods.

 

What are the stages involved in this process?

 

The first stage involves the drilling of a pilot hole. A small diameter pilot hole is first drilled along a pre-determined and drilling fluid is then pumped through a drill pipe to the drill bit. The drill bit and high-pressure jets grind the soil in the path of the drill stem. The drilling fluid also carries the cuttings, drilled soil, back to the entrance pit at the drill rig. It also reduces friction and stabilizes the drill hole.

 

The second step is the pre-reaming of the pilot hole. Here the pilot hole is then enlarged to a diameter that facilitates the pipe string pullback. A reamer is pulled back and rotated while pumping drilling fluid to cut and remove solids to enlarge the hole.

 

The final stage is the pipe pullback within the pre-reamed hole. As the pipe is pulled into the hole, drilling fluid is pumped downhole to provide lubrication to the pipe. This is generally how directional drilling works.