Air Percussion Drilling
Conventional Air Percussion drilling is used most frequently in the mineral and water exploration industry. The drill uses a pneumatic reciprocating piston-driven ‘hammer’ to drive a heavy drill bit into the rock. The drill bit is hollow, solid steel and has ~20 mm thick tungsten rods protruding from the steel matrix as ‘buttons’. The tungsten buttons are the cutting face of the bit.
The cuttings or “chips” are blown up the outside of the rods by compressed air or a combination of air and foam and collected at surface.
Air Percussion produces lower quality samples because the cuttings are blown up the outside of the rods and can be contaminated from contact with other rocks. At depths of more than 200metres water can cause the outside of the hole to become clogged with debris, preventing the drill cuttings from escaping the hole. With the use of drill enhancing fluids and proper drilling techniques, experienced drillers can drill to depths in excess of 500m.
Depending on the density and weight of the rock being drilled, the use of multiple high-powered air compressors, the Drill Crew is enabled drill deeper holes up to ~1250m.
Rotary Mud Drilling
In the direct-mud rotary drilling method, the borehole is advanced by rapid rotation of a drill bit mounted on the end of the drill rods. The bit cuts and breaks the material at the bottom of the hole into small pieces (cuttings). The cuttings are removed by pumping drilling fluid (water or water mixed with a fluid enhancer, such as bentonite) down through the drill rods and bit and up the annulus between the borehole and the drill rods. The drilling fluid also serves to cool the drill bit and stabilize the borehole wall, to prevent the flow of fluids between the borehole and surrounding earth materials, and to reduce cross-contamination between aquifers.
Direct-mud rotary drilling offers a number of advantages. It is a very fast and efficient means of drilling. Efficient rigs can produce several thousand feet of hole per day. The direct-mud rotary method can reach to several thousand feet in depth and create hole diameters greater than 48 inches. The method is adaptable to a wide range of geologic conditions. Only exceptionally large, poorly stabilized boulders or karst (cavernous) conditions are unsuited for direct-mud rotary drilling.
Sediment sampling is broadly supported in direct-mud rotary drilling. Standard split-barrel and thin-wall sampling are available in poorly lithified materials, while a broad range of coring equipment is supported for consolidated rock. Hydrologic conditions have little effect on direct-mud rotary drilling; operations usually are unhindered by the presence of ground water. Direct-mud rotary drilling readily supports the telescoping of casings to successively smaller sizes to isolate drilled intervals and to protect lower geologic units from contamination by previously drilled, contaminated upper sediments.
Despite some possible obstacles, direct-mud rotary drilling can be the best alternative, especially for deep wells or wells completed into well-lithified rocks. When the Drill Crew uses direct-mud rotary methods, hole diameters should be 3 inches to 5 inches larger than the outer diameter of the well casings to allow effective placement of filter and sealing materials. Two-inch diameter monitoring wells should, therefore, be installed within 5.5-inch or larger holes.
Odex is an excellent option when unconsolidated formations are too dense or cobbled for Auger Drilling. Odex drilling is a down-hole air hammer system that is designed to advance casing during drilling. Once a desired depth is reached they eccentric bit can be retrieved leaving the casing in place for sampling or installations.
As much as 90% of the land surface of the earth is covered with loose, unconsolidated material. When drilling in so-called overburden, the conditions are often challenging with risk of collapsing walls, hole deviation, and failure to reach design depth or bedrock. The casing advancement system is comprised of an ingeniously simple method of drilling through overburden while advancing the casing into the hole at the same time. This enables contractors the Drill Crew to perform work faster with higher quality and reduced risk. The system adds value whether the mission is to install foundation, support elements, or simply case the hole in collapsing formation.
Water well drilling is common in urban, developed areas where the well must be drilled quickly with minimum impact on the surrounding s. The Drill Crew offers a solution that can be used with compact rigs (using the Symmetrix system) with excellent results in almost any ground condition.
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