The standard method involves percussion drilling in which a drill is alternatively raised and dropped in the descending borehole. It is suited to the drilling of wells in any material from soft clay to the hardest rock.
[pdf] Reverse circulation is achieved by blowing air down the annulus of the rod, the differential pressure creating air lift of the water and cuttings up the inner tube which is inside each rod. It reaches the deflector.
[pdf] Reverse circulation is achieved by blowing air down the annulus of the rod, the differential pressure creating air lift of the water and cuttings up the inner tube which is inside each rod. It reaches the deflector.
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