Dear Madalin A ...

Dear Madalin

A “Down-the-Hole” Hammer is probably the most important component on the drill rig and the DTH system holds many advantages over other alternatives, for instance:  Rotary Drilling is fine for large diameter holes in softer more friable rock but less effective in hard rock or where small diameter holes are needed. Top Hammer (Drifter) drilling systems can produce satisfactory results for short hole drilling in hard homogenous rock conditions but would likely experience difficulty in deep holes and in soft ground with large diameters. The DTH system is by far the most versatile and can be used very successfully in a wide range of ground conditions from soft, through medium to very hard.

When you need to drill high quality holes with diameters between 100-254 mm, DTH (Down the Hole) drilling is by far the best and most effective method. DTH drilling can be performed in most types of rock, hard or soft. It's a commonly used method in the mining industry (blast hole drilling), water well drilling, construction, and in the oil and gas industry.

In DTH drilling, the drill string rotates while the drilling hammer continuously strikes down into the rock. Inside the hammer, a piston powered by compressed air gives the drill bit its striking power. This combined with the rotational movement means the rock is crushed in a very efficient manner.

The mechanical difference between the two types of drills is where the hammer is situated in the machine. The hammers applying repeated percussive pressure to the drill bits of DTH drills are situated in  direct contact  with the bit, and are thus actually ‘down-the-hole’. Top hammer drills, however, apply that pressure at the top of the drill string, outside of the hole.

Drilled wells are typically created using either top-head rotary style, table rotary, or cable tool drilling machines, all of which use drilling stems that are turned to create a cutting action in the formation, hence the term  drilling .

Drilled wells can be excavated by simple hand drilling methods (augering, sludging, jetting, driving, hand percussion) or machine drilling (rotary, percussion, down the hole hammer). Deep rock rotary drilling method is most common. Rotary can be used in 90% of formation types

Drilled wells can get water from a much deeper level than dug wells can—often up to several hundred metres.

Drilled wells with electric pumps are used throughout the world, typically in rural or sparsely populated areas,. Most shallow well drilling machines are mounted on large trucks, trailers, or tracked vehicle carriages. Water wells typically range from 3 to 18 metres  deep, but in some areas can go deeper than 900 metres.

Rotary drilling machines use a segmented steel drilling string, typically made up of 6 metres  sections of galvanized steel tubing that are threaded together, with a bit or other drilling device at the bottom end. Some rotary drilling machines are designed to install (by driving or drilling) a steel casing into the well in conjunction with the drilling of the actual bore hole. Air and/or water are used as a circulation fluid to displace cuttings and cool bits during the drilling. Another form of rotary style drilling, termed  mud rotary , makes use of a specially made mud, or drilling fluid, which is constantly being altered during the drill so that it can consistently create enough hydraulic pressure to hold the side walls of the bore hole open, regardless of the presence of a casing in the well. Typically, boreholes drilled into solid rock are not cased until after the drilling process is completed, regardless of the machinery used. Following steps may be taken-

1. Planning a Well.
2. Consider the costs and benefits of drilling a well against piping or shipping water in.
3. Know the specific location of the property where the well is to be drilled.
4. Find out what previous wells have been drilled on the property.
5. Consult geologic and topographic maps.
6. Ask people who live near the property.
7. Get assistance from a consultant.
8. Get whatever well-drilling permits you need.
9. Drill the well away from any potential contaminants.
10. Choose the appropriate construction method.

Wells are dug when there is sufficient water near the surface and no intervening dense rock. After a hole is made with shovels or power equipment, a casing is lowered into the aquifer, and the well is then sealed against contamination. As they are shallower than driven or drilled wells, they are more likely to go dry when drought lowers the water table.

1. Augers can be either rotating buckets or continuous stems and can be turned either by hand or with power equipment.
2. Rotary drills exude water based drilling fluid or compressed air from holes in a rotating bit to make drilling easier and pump out the drill cuttings.
3. Percussion cables work like pile drivers, with bit or tool moving up and down on a cable to pulverize the ground being drilled into
4. High-pressure water jets use the same equipment as rotary drills, without the bit, as the water both cuts the hole and lifts out drilled material. p and down on a cable to pulverize the ground being drilled into.
5. Once the well is drilled, casing is inserted to prevent the water from wearing away and being contaminated by the sides of the well.

 

Good Luck!

Prem Baboo