A
borehole is a narrow
shaft bored in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of
water, other liquids (such as
petroleum) or gases (such as
natural gas), as part of a
geotechnical investigation, environmental site assessment,
mineral exploration,
temperature measurement, as a pilot hole for installing piers or underground utilities, for geothermal installations, or for underground storage of unwanted substances, e.g. in
Carbon capture and storage.