Directional Drilling Definition and Uses

May 29, 2017


Directional drilling is defined in an engineer's handbook as a steerable boring technique. In other words, the technology mashes a standard vertically mounted drill with a horizontal directional drilling (HDD) system. Several engineering solutions paved the way for this guidable boring system, with oil drilling methods providing the best and most workable methods. Beginning with mud motors, here's a closer look at this trenchless drilling system.

Mud Motor Mastery

It's easy enough to drill a pilot hole into the ground at an angle and sink that drill deeper into the ground. At some point, though, that cut has to angle upward slightly so that it parallels the ground. Mud motors represent one such directional drilling solution. These progressive cavity mechanisms use a screwing action to burrow, then a control mechanism steers the helical rotor until it's cutting at the assigned angle. Variations on this theme include asymmetric drill heads and steerable flexible rods with special metal tips. In the case of that sophisticated mud motor, a liquefied mud is pumped down into the borehole to keep the unit moving. Meanwhile, the simple flexible rod is best suited for narrower directional channels. A surface guidance system, something like a metal detector, guides the routed rods while hydraulic power drives the flexible tubes deeper into the ground.

Determining Trench-Less Applications

There are helical rotors (Mud Motors) and drill heads with eccentric outlines, plus guidable rods. The directional drilling techniques then require a guiding hand on a control, a ground-based monitoring station, and a dirt removing fluid. That latter requirement pumps water or a water/bentonite mix into the routed borehole as a cuttings remover. The fluid also stabilises the recently excavated hole so that it's ready for the next stage. As for applications, a directional channel like this works best when a trench is prohibitively difficult or logistically impossible to dig. Under nature-conserved land, for example, pipes can run without disturbing the state-preserved flora and fauna. Another application for this directional boring method would be to pass several utility lines under a railroad crossing or a river.

In short, directional drilling equipment works best when there's already a structure or ground feature in place. The steerable tunnels pass under highways, rivers, and railway crossings without causing stoppages or expensive ground upheavals. Driven forward by well-established oil drilling technology solutions and newer steerable drill head products, all that's left to take care of after the steerable tool has cut its way into the ground is a system that removes the cuttings and stabilises the just excavated tunnel.

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