New technological advances and the use of preventive
measures can reduce the environmental impacts of drilling. Drilling is the
process of making a hole into a hard surface where the length of the hole is
very large compared to the diameter. In the context of mining engineering,
drilling refers to making holes into a rock’s mass. According to the Australian
mines atlas, drilling is used to obtain very detailed information about rock
type, mineral content, rock fabric and the relationships between rock layers
close to the surface and at depth.
The type of drill bit used in mining is dependent on the
type of drilling being done. There are three types of drilling:
1.
Percussion drilling – uses steel rock bits of
various designs to break up the rock while drilling.
2.
Reverse circulation- these drills produce rock
cuttings at the bit which are blown up the hole by compressed air. The cuttings
are separated from the air or water by a cyclone or cyclone-splitter
combination.
3.
Diamond drilling-using large machines is the
preferred method of delineating mineralization. Diamond drills produce core
which ranges from approximately one to two inches in diameter.
Drilling is one of the most intrusive aspects of
exploration. However, technological advances such as higher maneuver-ability
and productivity of drilling rigs, have the potential to significantly reduce
the impacts of drilling. Lighter rigs reduce ground compaction and allow
transport by helicopter. Increased efficiency of drilling equipment means less
time spent on the site and rehabilitation can start and end faster. Drilling
during the dry season reduces soil compaction and the potential for future
erosion.
When positioning drill holes and excavations, companies
should be aware of areas that are environmentally or culturally sensitive, as
identified in a pre-exploration baseline study or the Environment Impact
Assessment. Drill pads should be constructed with a nearby low drainage
collection area known as sump, to catch drainage from the storage of fuel, oil
and drilling fluid supplies. The sump should be located downhill from the drill
rig, and may need plastic lining, depending on the geology. Drilling fluids
should be recycled where possible, using separators to recover from the
drilling mud and cuttings.
Drilling equipment, including rigs and transport machinery,
should be maintained in good condition to prevent oil leaks and spills, all
equipment should be cleaned before using in a new area, as soul or traffic
movement can spread noxious weeds and kill local wildlife and plants.
The transport and storage of fuel and lubricants for
drilling equipment must also be handled with care. Fuel and lubricants should
be isolated in protected containers to prevent spillage and they should be
disposed of off-site according to the area’s regulations.
The refuelling or maintenance of equipment should be avoided
over natural water drainage lines and in sensitive habitats. Furthermore, all
drill rigs should have fire extinguishers and efficient exhaust pipes to reduce
potential for destructive brush fires. Equipment maintenance, fueling and
transport should be avoided during storms because rain exacerbates soil and
contaminant movement into waterways.
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