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.
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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.
Usually, contractors working on a dirt bore would pack up and move on to the next dirt bore when they encountered rock, leaving the rock boring for another contractor to complete.
With DTH drilling, contractors can change the drill that they were using for the current directional bore to a rock drill when they encounter rock by connecting the drill with a compressor and a steerable hammer.
Well drilling also needed changes to be made to rotary drilling when the well needed to take a turn.
DTH technique was used in well drilling exclusively to dig, accurate, vertical bores, and rotary drilling was used to turn the hole. The Directional DTH system, patented by Atlas Copco, was first used successfully in by drilling crews in the Marcellus Shale region of the United States to steer percussive drilling. Though the technology already existed, Atlas Copco succeeded in overcoming engineering challenges by modifying the design, such as:
Drilling in the gas plays of Appalachia in is a classic example where DTH pneumatic percussion drilling tools reduced the time and cost of a project in half. 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. With DTH, it was now possible to turn 2-4 degrees curves and drill the well&#;s tangent up to 30 degrees or greater averaging 300 feet per hour, where rotary drilling would progress 30-40 feet per hour.
The DTH system is easy and quick to adapt to a directional drill and is considered one of the best and most effective methods to drill high-quality holes that are stable and straight. It can be done on both hard and soft rock and is extensively used in the construction, oil and gas, and water well industries.
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.
This action along with the rotational movement of the drill string crushes the rock efficiently. Since the piston strikes directly on the bit, energy transfer takes place down the hole with minimum loss of energy, allowing drilling to greater depths.
The driving medium i.e. compressed air is also the flushing medium. The flushing medium (in some cases, water is also used) is pressed down through the drill pipes, down-the-hole hammer and the drill bit. It is then forced back out of the borehole along with the cuttings through the annular gap between the drill pipe and the borehole.
Below are few of the many benefits associated with DTH drilling:
The DTH method is the most productive and cost-effective method. It is environmentally friendly, as it produces lesser noise and vibration compared to other drilling methods making it ideal for cities.
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It also leaves a lesser carbon footprint as it uses low amounts of drilling mud and additives, reducing the amount of drilling fluid that needs to be recycled and disposed of, in turn reducing the number of trips required for disposal of used mud.
This technology will help contractors do more in lesser time at lesser cost and help keep ahead in a very competitive market.
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Down-the-hole drilling (DTH) essentially involves a drilling hammer at the bottom of a drill string. It relies on three elements for drilling holes: bit loading (weight), rotation and air. These active elements combine to be efficient at crushing rock. As the drill string slowly rotates, the drilling hammer is forced into the rock repeatedly. Striking power is provided by compressed air driving a piston inside the hammer.
DTH drilling is often used in the mining industry (blast hole drilling), on construction sites, drilling water wells, and in the oil and gas industry.
DTH drilling offers several advantages over top-hammer drilling for larger, deeper holes in medium-hard formations. Because the hammer is at the bottom of the hole, power loss is minimal as the hole deepens. That means energy is not lost in the drill string and penetration rates do not markedly decline with depth&#;provided that back pressure does not rise significantly in the borehole. DTH drilling is most suitable for hole diameters of 4&#;10 inches, with some exceptions.
The DTH hammer is pneumatically powered, with the compressed air propelling it forward to impact and fracture rock. Compressed air also travels through the drill bit into the hole (air exhaust), which blows the chips and dust out of the hole.
From environmental and social perspectives, DTH is a good option because it produces much less noise and vibration than many other drilling methods. Quieter drilling means it is often the preferred drilling method when used in cities and populated areas.
FRD USA offers Tier IV and Tier III (for Central America/the Caribbean) DTH drills. Learn more here or contact us at 800.358..
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