borehole

thumb|Borehole digging for a borewell or tube wellthumb|Borewell diggingthumb|upright|A woman in Uganda collects water from a borehole and attached hand pump thumb|A drilled well in Ghana; the borehole is not visible

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 (drilled water well and tube well), other liquids (such as petroleum), or gases (such as natural gas). It may also be 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.