Borehole

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.

Samples collected from boreholes are often tested in a laboratory to determine their physical properties, or to assess levels of various chemical constituents or contaminants.

This also helps prevent surface contaminants from entering the borehole and protects any installed pump from drawing in sand and sediment.

The British sinologist and historian Michael Loewe states that borehole sites could reach as deep as 600 metres (2,000 ft).

[4][5] A Western Han dynasty bronze foundry discovered in Xinglong, Hebei had nearby mining shafts which reached depths of 100 metres (330 ft) with spacious mining areas; the shafts and rooms were complete with a timber frame, ladders and iron tools.

From 2011 until August 2012 the record was held by the 12,345-metre (40,502 ft) long Sakhalin-I Odoptu OP-11 Well, offshore the Russian island Sakhalin.

The machinery and techniques to advance a borehole vary considerably according to manufacturer, geological conditions, and the intended purpose.

To prevent the walls from collapsing and to ensure water quality, the borehole is lined with materials like bricks, stones, or concrete rings.