About Directional Drilling

Directional Drilling; the process of controlling the direction, or path, of a drill hole. 

Directional Drilling is the process of controlling the direction, or path, of a drill hole with the aim of either preventing deviation, or intentionally deviating the drill path to avoid obstacles such as previously drilled holes or to intersect a predetermined target. The main industries where directional drilling techniques are employed are Oil and Gas, Civil Construction and Mining.

The Oil and Gas industry uses directional drilling primarily to improve access to oil or gas reservoirs by increasing the length of the well in the target zone or to access a number of targets from the one "parent' well.

In addition directional drilling techniques are often applied in the coal bed methane market. Methane gas (sequestered in coal seams) is a hazard to underground coal miners and needs draining prior to mining; additionally it is also a potential source of energy. Gas drainage may be undertaken for either or both of these reasons. Gas drainage operations carried out from the surface entail drilling a hole down into a horizontal (or near horizontal) coal seam and then along the seam typically for 1200m or more horizontally. When the hole is completed and dewatered, the redced hydrostatic head allows methane gas to migrate from the coal into the drill hole where it is pumped to surface for collection.

The utilities industry makes use of directional drilling techniques for installing cables and pipes underground without the need for surface excavation (commonly called 'trenchless" technology). This method has become widespread as it offers a much reduced environmental impact as well as convenience and cost savings. One of the more ambitious applications of this technology is to drill beneath rivers or estuaries up to two kilometres wide crossing below the river bed, usually with an exit point accuracy of a few metres.

The mining industry makes use of directional drilling techniques when delineating a deep ore body. Often nickel and gold targets underground can be relatively small, thus requiring a high degree of drilling accuracy. Given that drill-holes can deviate substantially, guiding the hole to a target is very important. Another application in the mining industry is multiple target intersection, where one hole is "side-tracked" off another and a second (or third) target is intersected. This practice can result in substantial cost savings as the top section (anything from 400m to 1500m) of a hole need only be drilled once even though several targets are intersected by a number of side-tracked holes.

In all of the above industries, fundamentally similar equipment is used. A steerable "downhole motor" followed by an MWD (measurement while drilling) system which transmits directional data to the surface, where it can be analysed enabling steering decisions to made. Changes in direction are made by rotating the drill string and "pointing" the downhole motor in the desired direction.

Directional drilling is an expanding industry with new tooling and techniques being constantly developed.