Horizontal Directional Drilling

 Horizontal Directional Drilling (HDD), also known as Directional Boring, horizontal drilling, slant drilling, or deviated drilling, is a method of trenchless technology. In the oil and gas industry, directional boring involves laterally drilling of various wells through a zone of oil or gas-bearing rock at angles from a vertical well-hole.

Directional Boring or Horizontal directional drilling is also used in the installation of utility pipelines and conduits. A pilot borehole is drilled along a pre-determined bore path from the surface with minimum disturbance. Directional Boring is mainly used for making crossings under rivers, roads and existing structures, with the purpose of installing pipes and conduits to transport different types of fluids and materials.

Directional Boring or Horizontal directional drilling is a way to get utilities from one point to anotherwithout destroying the existing ground or obstacles that are in between the two points. Directional drilling goes above and beyond traditional trenching; connecting utilities and services in places that traditional trenching is impossible.

HDD Excecution

The Horizontal Directional Drilling itself is divided onto 3 steps, which are :

Ø  Pilot Hole Drilling

(reference : www.mears.net)

Drilling the hole from entry-side to exit-side through the soil under the river, first, the drilling bit drills and open the way, while a mud (consists of bentonite and other materials) is injected through the drilling rod and out from the drilling bit, functioning as a lubricant and clearing the residual materials produced by the drilling bit. Bentonite functioning as a preventive chemical unsure that is spread around the hole and preventing the soil from collapsing, preventing water and poisonous gas to go through the hole while drilling.

During drilling process, the viscosity of the mud is being controlled, so that the mud viscosity meets the requirements. The residual mud is recycled through a recycling facility so that the bentonite can be used later by separating the residual materials produced from drilling process and the bentonite, which will be recycled later. The bit is equipped with a tracking device the position, so that the drilling process go through the planned way.

Two tracking devices are used, as follows :

-          The main tracking equipment installed in the drilling bit, transmitting the magnetic force to be checked by the second equipment;

-          The secondary equipment for position correcting

Ø  Reaming

Once the bit and the drilling case arrive on the exit side planned, the bit and the drilling rod are packed out for the reamer installation. The reamer’s function is to enlarge the hole the pilot drill made. While the reaming, the mud is also injected through and out from the reamer. In this process, the mud recycling process also occurs.

Ø  Pulling Back

During reaming, the pipe pulling process is also executed, the pipe is connected to the second reamer a  pulling head, the pipe is also rotating in the opposite way from the reamer. In this process, swivel is used to minimize the impact from the reamer, thus the reamer rotation will not interfere the pipe rotation.

(reference : www.mears.net)

Directional Boring :Comparing Against Traditional Method

Open cut, or trenching, is the most common way to install and connect utilities, but it has some limitations. This method can only be used when the ground above the utilities can be disturbed and there are no buildings, roadways or other obstructions in the way. Directional Boring can be used in the same situation where open cut is planned, but it can also be used to go under roads, sidewalks, rivers, even houses if there is a need for it.

The installation cost for trenching versus Directional Boring is usually lower, in the range of 6 to 8 times less than horizontal drilling. These two technologies usually compliment each other; trenching or plowing being more cost effective but having limitations and directional boring taking care of everything else but at a higher cost. If we wanted to choose one over the other without cost as a factor, Directional Boring or horizontal directional drilling would be selected as the best alternative; doing everything trenching and plowing can do and doing jobs once thought impossible before this great technology.

Construction Footprint of Directional Boring

Directional Boring usually has a lower impact on the existing ground; meaning a lot less of the existing is disturbed. There is still damage that is done as with all construction equipment, but proper planning and patience can keep it to a minimum. The horizontal directional drilling machines are heavy, run on tracks and tend to disturb or damage the area below them or where they transit.

Another area that will cause some trouble is the water used for the boring. The water will usually tend come up to the surface of the ground. It normally causes minimal disturbances but can be a situation where sod or grass seed needs to be replaced in those areas. For the most part, horizontal directional drilling will only disturb the location the machine is set up at and any place that utilities need to be connected. In some circumstances, a drill can be set up on the side of the road, and the only disturbance will be from the footprints of the locator. If you are looking for minimal damage to your existing ground, Directional Boring is the method to be used.

Directional Boring Benefits

• Reduced soil disturbance.
• A single location area can be used to install different pipes.
• Reduces the fractures to existing rock formations.
• Reduces the contamination of groundwater pollution.
• Protects the ecosystem and adjacent areas.
• Directional drill produces twice the amount of oil or gas being extracted.
• Reduces the excavation and shoring costs.
• It is a safer operation than open cut.
• Weather will not impact directly on the process.
• Limited traffic and landscape disruption. Ideal for sites sensitive to surface disruption such as heavy roadways, airport runways, golf courses, etc.
• Ability to drill beneath surface obstructions or ongoing site operations.

Reference : 

http://construction.about.com/od/Special-Construction/a/Horizontal-Directional-Drilling.htm

Arya Pamungkas dkk. 2012. On-the-job Training Report : Metode Instalasi Pipa River Crossing 4 di Muara Kaeli dengan Metode Horizontal Directional Drilling.