Patent classifications
E
FIXED CONSTRUCTIONS
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E21
EARTH OR ROCK DRILLING; MINING
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E21B
EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
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21/00
Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
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E21B21/08
Controlling or monitoring pressure or flow of drilling fluid, e.g. automatic filling of boreholes, automatic control of bottom pressure
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E21B21/085
Underbalanced techniques, i.e. where borehole fluid pressure is below formation pressure
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