For power head rig, from up to down: taps, power head, air box, double-wall drill pipe, the air-water mixer, single-wall drill pipe and drill bit.
For turn plate rig, from up to down: double-channel air-water taps, double-wall drill pipe initiative, the double-wall drill pipe, the air-water mixer, single-walled drill pipe and drill bit.
2 The process principle
For example the power head rig, compressed air through the air box into the annular gap of the double-wall drill pipe and reach the air-water mixer along the annular gap, through the air-water mixer and the water inner tube mixed to air-water mixture, its specific gravity is far less than water, which can reduce the water level in tube, make the water level in inner tube higher than the water level between bore wall and the drill pipe.In the role of water level,the water between bore wall and the drill pipe inflow to the Drill pipe tube,and carrying debris from the inner tube back, thus forming air lift reverse circulation.
3 technical characteristics:
a. Compare with normal circulation drilling, due to rock debris back quickly from the inside pipe, ability to carry rock debris, bore bottom clean, thus greatly improve the drilling efficiency; Because by the bore wall less pressure, not easy jam rock frature, thus large volume of water as well.
b. Compare with full reverse circulation, use less double-wall drill pipe, reduce the investment of the drill pipe.
c. Compare with full reverse circulation, drilling when high water level, use a lower pressure air compressor, reduce the investment of the equipment.
d. Generally drilling with tri-cone bit, also can use scraper bit and PDC bit drilling, but not with Pneumatic DTH hammer drilling.
e. With the power head drilling rig, rotary drilling rig to use.
4 Applicable range:
a. Suitable for including for complex ground of drilling wells, use the slurry as flushing liquor in easy slump strata in order to protect the bore wall.
b. Suitable for drilling in air discharge wells,coal-bed gas well and Shale gas well.
c. Don't suitable for drilling in dry and loss formation to drilling.