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A borehole is a narrow
shaft Shaft may refer to: Rotating machine elements * Shaft (mechanical engineering), a rotating machine element used to transmit power * Line shaft, a power transmission system * Drive shaft, a shaft for transferring torque * Axle, a shaft around whi ...
bored In conventional usage, boredom, ennui, or tedium is an emotional and occasionally psychological state experienced when an individual is left without anything in particular to do, is listlessness and dissatisfaction arising from a lack of occup ...
in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of
water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...
( drilled water well and tube well), other liquids (such as
petroleum Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...
), or gases (such as
natural gas Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbon d ...
). It may also be part of a
geotechnical investigation Geotechnical investigations are performed by geotechnical engineers or engineering geologists to obtain information on the physical properties of soil earthworks and foundations for proposed structures and for repair of distress to earthworks a ...
, environmental site assessment,
mineral exploration Mining in the engineering discipline is the extraction of minerals from underneath, open pit, above or on the ground. Mining engineering is associated with many other disciplines, such as mineral processing, exploration, excavation, geology, and ...
,
temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...
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 Carbon capture and storage (CCS) or carbon capture and sequestration is the process of capturing carbon dioxide (CO2) before it enters the atmosphere, transporting it, and storing it (carbon sequestration) for centuries or millennia. Usually th ...
.


Importance

Engineer Engineers, as practitioners of engineering, are professionals who Invention, invent, design, analyze, build and test machines, complex systems, structures, gadgets and materials to fulfill functional objectives and requirements while considerin ...
s and
environmental consultant Environmental consulting is often a form of compliance consulting, in which the consultant ensures that the client maintains an appropriate measure of compliance with environmental regulations. There are many types of environmental consultants, b ...
s use the term ''borehole'' to collectively describe all of the various types of holes drilled as part of a
geotechnical investigation Geotechnical investigations are performed by geotechnical engineers or engineering geologists to obtain information on the physical properties of soil earthworks and foundations for proposed structures and for repair of distress to earthworks a ...
or environmental site assessment (a so-called Phase II ESA). This includes holes advanced to collect soil samples, water samples or rock cores, to advance ''
in situ ''In situ'' (; often not italicized in English) is a Latin phrase that translates literally to "on site" or "in position." It can mean "locally", "on site", "on the premises", or "in place" to describe where an event takes place and is used in ...
'' sampling equipment, or to install monitoring wells or piezometers. 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. Typically, a borehole used as a
water well A well is an excavation or structure created in the ground by digging, driving, or drilling to access liquid resources, usually water. The oldest and most common kind of well is a water well, to access groundwater in underground aquifers. T ...
is completed by installing a vertical pipe (casing) and well screen to keep the borehole from caving. This also helps prevent surface
contaminants Contamination is the presence of a constituent, impurity, or some other undesirable element that spoils, corrupts, infects, makes unfit, or makes inferior a material, physical body, natural environment, workplace, etc. Types of contamination ...
from entering the borehole and protects any installed pump from drawing in sand and sediment. Oil and natural gas wells are completed in a similar, albeit usually more complex, manner. As detailed in
proxy (climate) In the study of past climates ("paleoclimatology"), climate proxies are preserved physical characteristics of the past that stand in for direct meteorological measurements and enable scientists to reconstruct the climatic conditions over a longer ...
, borehole temperature measurements at a series of different depths can be effectively " inverted" (a mathematical formula to solve a matrix equation) to help estimate historic surface temperatures. Clusters of small-diameter boreholes equipped with heat exchangers made of plastic PEX pipe can be used to store heat or cold between opposing seasons in a mass of native rock. The technique is called
seasonal thermal energy storage Seasonal thermal energy storage (STES), also known as inter-seasonal thermal energy storage, is the storage of heat or cold for periods of up to several months. The thermal energy can be collected whenever it is available and be used whenever nee ...
. Media that can be used for this technique ranges from gravel to bedrock. There can be a few to several hundred boreholes, and in practice, depths have ranged from 150 to 1000 feet.


History

Borehole drilling has a long history. By at least the Han Dynasty (202 BC – 220 AD), the Chinese used deep borehole drilling for mining and other projects. The British sinologist and historian Michael Loewe states that borehole sites could reach as deep as 600 m (2000 ft).Loewe (1968), 194. K.S. Tom describes the drilling process: "The Chinese method of deep drilling was accomplished by a team of men jumping on and off a beam to impact the drilling bit while the boring tool was rotated by buffalo and oxen."Tom (1989), 103. This was the same method used for extracting
petroleum Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...
in
California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...
during the 1860s (i.e. "Kicking Her Down"). A Western Han Dynasty bronze foundry discovered in Xinglong,
Hebei Hebei or , (; alternately Hopeh) is a northern province of China. Hebei is China's sixth most populous province, with over 75 million people. Shijiazhuang is the capital city. The province is 96% Han Chinese, 3% Manchu, 0.8% Hui, and ...
had nearby mining shafts which reached depths of 100 m (328 ft) with spacious mining areas; the shafts and rooms were complete with a timber frame, ladders and iron tools.Loewe (1968), 191.Wang (1982), 105. By the first century BC, Chinese craftsmen cast iron drill bits and drillers were able to drill boreholes up to 4800 feet (1500 m) deep. By the eleventh century AD, the Chinese were able to drill boreholes up to 3000 feet in depth. Drilling for boreholes was time-consuming and long. As the depth of the holes varied, the drilling of a single well could last nearly one full decade.Tom (1989), 103. It wasn't up until the 19th century that Europe and the West would catch up and rival ancient Chinese borehole drilling technology. For many years, the world's longest borehole was the Kola Superdeep Borehole in Russia. From 2011 until August 2012 the record was held by the long
Sakhalin-I The Sakhalin-I (russian: Сахалин-1) project, a sister project to Sakhalin-II, is a consortium for production of oil and gas on Sakhalin Island and immediately offshore. It operates three fields in the Okhotsk Sea: Chayvo, Odoptu and Ark ...
Odoptu OP-11 Well, offshore the Russian island
Sakhalin Sakhalin ( rus, Сахали́н, r=Sakhalín, p=səxɐˈlʲin; ja, 樺太 ''Karafuto''; zh, c=, p=Kùyèdǎo, s=库页岛, t=庫頁島; Manchu: ᠰᠠᡥᠠᠯᡳᠶᠠᠨ, ''Sahaliyan''; Orok: Бугата на̄, ''Bugata nā''; Nivkh ...
.Sakhalin-1 Project Drills World's Longest Extended-Reach Well
The Chayvo Z-44 extended-reach well took the title of the world's longest borehole on 27 August 2012. Z-44's total measured depth is 12,376 m (40,604 ft). However, ERD wells are more shallow than the Kola Borehole, owing to a large horizontal displacement.


Methodology

Drillers may sink a borehole using a drilling rig or a hand-operated rig. The machinery and techniques to advance a borehole vary considerably according to manufacturer, geological conditions, and the intended purpose. For
offshore drilling Offshore drilling is a mechanical process where a wellbore is drilled below the seabed. It is typically carried out in order to explore for and subsequently extract petroleum that lies in rock formations beneath the seabed. Most commonly, the t ...
floating units or platforms supported by the seafloor are used for the drilling rig.


See also

* Askam Borehole in Pennsylvania * Casing cutter *
Deep borehole disposal Deep borehole disposal (DBD) is the concept of disposing high-level radioactive waste from nuclear reactors in extremely deep boreholes instead of in more traditional deep geological repositories that are excavated like mines. Deep borehole dispos ...
* Hole opener * Horizontal drillhole disposal * Kola Superdeep Borehole * Vertical seismic profile


References


External links


Boreholes: Swiss Geological Survey
{{Man-made and man-related Subterranea Chinese inventions Drilling technology Hole making