The HDD technology is an underground drilling method that involves the use of HDD directional drilling machines. These machines drill a tunnel/ hole along a predetermined bore path into which a pipe or cable is inserted. Horizontal Directional Drilling in no dig industry is of great importance as it has replaced the traditional method and is not used to install underground pipelines, cables, and service conduit via trenchless methods.
How Does The HDD Technology Work?
Although this method has evolved over the last couple of decades, the concept still remains the same. Basically, the holes are drilled at an angle (never vertically) and there may be multiple holes drilled from the same entry point. This goes a long way in minimizing the environmental impact.
The HDD technology utilizes a three stage process. These stages are:
- Pilot Hole
The first step involves the digging of a pilot hole that usually has a small diameter. The drilling fluid is then dumped inside the drill pipe up to the drill bit. The fluid comes out in a high-pressure jet that makes the soil softer before the drill grinds through. The fluid also carries the cuttings back to the hdd drilling machinery through the entrance pit.
The pilot hole needs to be tracked either using a walkover guidance system or a wire-line magnetics system. The tracking depends on how large the hole is; the former method is used to track smaller pilot holes while the latter is used to track larger pilot holes. Both tracking methods make use of a transmitter that is located near the drill head to send signals to the location engineer. The engineer is able to get the exact coordinates of the drill stem. This helps the team to maneuver under there without really being there. Once it reaches the exit point, the drilling bit is replaced with a reamer.
This second step entails enlarging the pilot hole into a size that is large enough for the pipes and cables to fit in. The reamer goes through the hole while pumping drilling fluid in order to remove solids from there. To ensure that the holes is clear and stable to avoid collapse, Bentonite is used alongside other additives. Bentonite forms a layer around the hole that not only helps with stability but also prevents fluid loss or infiltration. The additives that are used together with Bentonite are usually polymers and their function is to help break up the clay soil that can prove to be quite difficult to drill though. An evenly mixed drilling fluid is key in making sure that there are no blockages occurring inside the tunnel either while it’s still being dug or after completion
- Pipe Pullback
The last step is the pullback of the pipe within the pre-reamed hole. As the pipe is being laid down, the hdd drilling fluid is pumped to aid in lubrication. To prevent any torsional stress from the rotating drill string, the drill rod and reamer are attached to a swivel. The swivel is placed between the pipe and the reamer.
Major improvements in the HDD technology have come a long way and are helping researchers to make clever improvements in the world of drilling. Today, for example, the drilling angle and the path of the tunnel can be controlled at high precision levels thanks to the innovative technologies. This has provided the world of drilling with many solutions to the challenges that they face. These solutions increase the machine’s efficiency while cutting down on wastage and costs.