As the evolution of drill rig continues throughout the years, the need for directional drill rigs came with a slow realization that not all oil wells are vertical. There is also the need of drilling in around existing pipes or utilities, and that pushed the development of directional drilling rig. Directional boring, also known as horizontal directional drilling (HDD) is one of the latest methods used to install infrastructure like power cable conduits, gas lines, oil lines, sewer lines, water lines, product pipelines, telecom and environmental casing. It has minimal impact on the environment and surroundings. By using a surface launched rig, the drill bit maneuvers in and around the subsurface in a shallow arc radius, following a planned flight path that is supposed to avoid any underground geological restriction. The drilling process is also aided with the continuous supply of slurry mixture that is pumped through the drill bits as the drilling occurs. This viscous fluid helps facilitate the removal of cuttings, stabilize the bore hole, cool the cutting head, and lubricate the passage of the product pipe.

There are 3 types of locating system to help navigate the drill head. There is the walk-over system which uses a transmitter that is located at the back of the bore head to register angle, rotation, direction and temperature. There is also the wire-line system which uses magnetic guidance system. Lastly, the gyro-guided system, where a full inertial navigation system is located close to the drill head. This system is completely autonomous and by far the most accurate one. Each locating system has its own unique advantages and is selected based on job size and site condition.

A successful directional boring for utility installation requires three stages. First, a small sized drill bit is launched into the subsurface from the starting point. It will follow a predetermined path that was given by the geologists and engineers, and resurface at the end point. Second, at the end point, a drill bit with a larger diameter called a back reamer is attached, and the drill bit is sent backwards, following the same path it took back to the starting point. This is to enlarge the bore holes done in the first phase. Lastly, the pipeline is pulled through the holes created previously, hence creating a continuous underground pipeline. This technique is very useful as it does not require the construction crew to dig out the whole path of the pipeline to install them. With this method, installation can be done with less traffic disruption, lower cost, less time, and reduced environmental impact.

However, the use of this method requires the operator to have all the information of the utilities layout of the area before proceeding. Uncoordinated and unguided directional drilling can lead to severe damage; Therefore, it is best to call in to the local utilities locator before the start of work.

The picture below is of the starting pit of a trench-less directional drilling:

The fluids in there are the drilling fluid, which is a mixture of water and bentonite.

To learn more about the HDD process, click on the link below to get more information:

https://en.wikipedia.org/wiki/Directional_boring

You can also check out this video made by Directional Technologies that showcases the process of directional boring:

There are a few suppliers out there that are renting/selling this equipment, if you are interested, links to a couple of the suppliers are listed. The specs and the capability of the drilling rigs can be found on the site.

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