What is a down-the-hole drill?

A down-the-hole drill, usually called DTH by most professionals, is basically a jackhammer screwed on the bottom of a drill string. The fast hammer action breaks hard rock into small cuttings and dust that are evacuated by a fluid (air, water or drilling mud). The DTH hammer is one of the fastest ways to drill hard rock.

What is down-the-hole (DTH) drilling?

Down-the-hole (DTH) drilling has made it easier for contractors to drill wells faster and more efficiently, and to transition from dirt boring to rock boring just by adding a compressor and hammer to the drill bit.

How was a hole drilled?

This system could not guarantee a finished hole size and only pure vertical holes could be drilled as the system basically relied on gravity. Debris from the hole was baled out using a baling tube with a clack valve, which was periodically dropped on a winch to capture the slurry, which was then brought to the top of the hole to be discharged.

How long did it take to drill a 12,000 ft hole?

The original estimate for completion of a 12,000-foot hole was 30 days using the conventional rotary technique, which was reduced to 13 days using the DTH method. Before DTH was used, drillers would typically case the vertical portion of the well and convert to rotary drilling to drill at a tangent.

How do you drill a rock with a DTH hammer?

This method is mainly applied for hard to very hard rock and/or for penetrating large boulders. 1. Setting the DTH hammer with drill rod and casing on the drilling point. 2. Rotary and percussive drilling of the drill string under compressed air supply. 3. After reaching the final depth, unlocking of the drill rod with DTH hammer and pilot bit.

How does a DTH drill work?

DTH equipment consists of a drilling hammer and a piston-powered by compressed air. As the drill string rotates, the drilling hammer strikes down on the rock. The drill bit receives its striking power from a piston inside the hammer that is powered by compressed air.