borehole
geological science
Learn about this topic in these articles:
mineral exploration
- In Earth exploration
The deepest borehole so far drilled extends only to a depth of about 10 kilometres (6 miles). Because direct exploration is so restricted, investigators are forced to rely extensively on geophysical measurements (see below Methodology and instrumentation).
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oil drilling
- In petroleum production: Cable tooling
The borehole had to be free of liquids during the drilling so that the bit could remove rock effectively. This dry condition of the hole allowed oil and gas to flow to the surface when the bit penetrated a producing formation, thus creating the image of…
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