HDD also known as directional boring, directional drilling, horizontal drilling, or slant drilling, is a method of treachless technology. In oil & gas industry, it is used to access to the oil & gas bearing reservior from a laterally vertical well. It can also be used for utilites to get cross from one point to another without distroying the existing ground or obstacles, usully crossing under rivers, road, roadway, and other existing structures. Drilling mud circulation system would also be used to smooth directional drilling processing.

Horizontal Directional Drilling

 
For horizontal directional drilling (HDD), a drilling path should be pre-ditermined from the surface of the ground with a minimum disturbance. A pilot borehole is then drilled by reamer along the drilling path. The purpose of directional drillig is mainly to install & connect pipes & conduits to transport different type of fluids & other material. As directional drilling is often not much deep, mainly boring the surface formation, so it mainly use water or water based drilling fluids to suspend and carry the drilled solids to the surface of the ground.

Directional drilling for utilites is often much faster than oil & gas drilling. A quick movable drilling mud system is often needed. Different from oil drilling mud system which is normally placed directely on the ground, HDD mud system normally has wheels to move, and draged by a tractor. While on the removable solids control system  solids control  solids control equipment drilling fluid cleaning system  shale shaker  desander  desilter   centrifuge .