Kola Superdeep Borehole

Coordinates: 69°23′47″N 30°36′36″E / 69.3965°N 30.6100°E / 69.3965; 30.6100
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Kola Superdeep Borehole
Superstructure of the Kola Superdeep Borehole, 2007
Kola Superdeep Borehole is located in Russia
Kola Superdeep Borehole
Kola Superdeep Borehole
Location of the borehole in Murmansk Oblast, Russia
Kola Superdeep Borehole is located in Murmansk Oblast
Kola Superdeep Borehole
Kola Superdeep Borehole
Kola Superdeep Borehole (Murmansk Oblast)
LocationPechengsky District
ProvinceMurmansk Oblast
Coordinates69°23′47″N 30°36′36″E / 69.3965°N 30.6100°E / 69.3965; 30.6100
TypeScientific borehole
Greatest depth12,262 metres (40,230 ft)
  • 1970–1983
  • 1984
  • 1985–1992

The Kola Superdeep Borehole (Russian: Кольская сверхглубокая скважина, romanizedKol'skaya sverkhglubokaya skvazhina) SG-3[a] is the result of a scientific drilling project of the Soviet Union in the Pechengsky District, near the Russian border with Norway, on the Kola Peninsula. The project attempted to drill as deep as possible into the Earth's crust.

Drilling began on 24 May 1970 using the Uralmash-4E, and later the Uralmash-15000 series drilling rig, and it became the deepest manmade hole in history in 1979. The 23-centimetre-diameter (9 in) boreholes were drilled by branching from a central hole.[1] The deepest reached 12,262 metres (40,230 ft; 7.619 mi) in 1989, the deepest human-made hole on Earth, and remains so as of 2024.

In terms of true vertical depth, it remains the deepest borehole in the world. For two decades, it was also the world's longest borehole in terms of measured depth along the well bore (that is, borehole length) until it was surpassed in 2008 by the 12,289-metre-long (40,318 ft; 7.636 mi) Al Shaheen Oil Well in Qatar.[2]


Kola Superdeep Borehole, commemorated on a 1987 USSR stamp

Drilling began on 24 May 1970 using the Uralmash-4E, a serial drilling rig used for drilling oil wells. The rig was slightly modified to be able to reach a 7,000-metre (23,000 ft) depth. In 1974, the new purpose-built Uralmash-15000 drilling rig was installed onsite, named after the new target depth, set at 15,000 metres (49,000 ft).[3]

On 6 June 1979, the world depth record held by the Bertha Rogers hole in Washita County, Oklahoma, United States, at 9,583 metres (31,440 ft),[4] was broken. In October 1982, the first hole reached 11,662 metres (38,261 ft),[5] and the second hole was started in January 1983 from a 9,300-metre (30,500 ft) depth of the first hole.[3]

In 1983, the drill passed 12,000 metres (39,000 ft) in the second hole, and drilling was stopped for about a year for numerous scientific and celebratory visits to the site.[6]

This idle period may have contributed to a breakdown after drilling resumed; on 27 September 1984, after drilling to 12,066 metres (39,587 ft), a 5 metres (16 ft) section of the drill string twisted off and was left in the hole. Drilling was restarted in September 1986, 7,000 metres (23,000 ft) from the first hole.[6][5]

The third hole reached 12,262 metres (40,230 ft) in 1989.[7] In that year, the hole depth was expected to reach 13,500 metres (44,300 ft) by the end of 1990 and 15,000 metres (49,000 ft) by 1993.[8][9][failed verification]

In June 1990, a breakdown occurred in the third hole at 12,262 metres (40,230 ft) of depth. The drilling of the fourth hole was started in January 1991 from 9,653 metres (31,670 ft) of depth of third hole. The drilling of the fourth hole was stopped in April 1992 at 11,882 metres (38,983 ft) of depth. Drilling of the fifth hole started in April 1994 from 8,278 metres (27,159 ft) of depth of the third hole. Drilling was stopped in August 1994 at 8,578 metres (28,143 ft) of depth due to lack of funds and the well itself was mothballed.[5][10]


The Kola Superdeep Borehole penetrated about a third of the way through the Baltic Shield continental crust, estimated to be around 35 kilometres (22 mi) deep, reaching Archean rocks at the bottom.[11] The project has been a site of extensive geophysical examinations. The stated areas of study were the deep structure of the Baltic Shield, seismic discontinuities and the thermal regime in the Earth's crust, the physical and chemical composition of the deep crust and the transition from upper to lower crust, lithospheric geophysics, and to create and develop technologies for deep geophysical study.

During the drilling process, the expected basaltic layers at seven kilometers down were never found, nor were basaltic layers at any depth.[12] There were instead more granites, deeper than predicted. The prediction of a transition at seven kilometers was based on seismic waves indicating discontinuity, which could have been caused by a transition between rocks, or a metamorphic transition in the granite itself.[12] In fact, in another unexpected finding, water pooled three to six kilometers below the surface,[12][13] having percolated up through the granite until it reached a layer of impermeable rock.[14][15] This water did not naturally vaporize at any depth in the borehole.[16]

Microscopic plankton fossils were found six kilometres (3.7 mi) below the surface.[1]

Another unexpected discovery was a large quantity of hydrogen gas. The drilling mud that flowed out of the hole was described as "boiling" with hydrogen.[17]

In 1992, an international geophysical experiment obtained a reflection seismic crustal cross-section through the well. The Kola-92 working group consisted of researchers from the universities of Glasgow and Edinburgh in the United Kingdom, the University of Wyoming in the United States, and the University of Bergen in Norway, as well as several Russian earth science research institutions.[18] The experiment was documented in a video recorded by Professor David Smythe,[19] which shows the drilling deck in action during an attempt to recover a tool dropped down the hole.


The borehole site in 2012
The borehole (welded shut), August 2012

The drilling ended in 1995 due to a lack of funding.[10] The scientific team was transferred to the federal state unitary subsidiary enterprise "Kola Superdeep," downsized, and given the new task of thoroughly studying the exposed section.[5] In 2007, the scientific team was dissolved and the equipment was transferred to a private company and partially liquidated.[5]

In 2008, the company was liquidated due to unprofitability,[20] and the site was abandoned. It is still visited by sightseers, who report that the structure over the borehole has been partially destroyed or removed.[21]

Similar projects[edit]


The Kola Superdeep Borehole was both the longest and deepest borehole in the world from 1989 to 2008.[1] In May 2008, the Kola Superdeep Borehole's record length (but not record depth) was surpassed by a curved borehole of the extended reach drilling well BD-04A in the Al Shaheen Oil Field in Qatar, with a total length of 12,289 metres (40,318 ft) and a horizontal reach of 10,902 metres (35,768 ft).[27][28] In terms of depth below the surface, the Kola Superdeep Borehole SG-3 retains the world record at 12,262 metres (40,230 ft) reached in 1989 and is still the deepest artificial point on Earth.[29]

See also[edit]


  1. ^ SG (СГ) is a Russian designation for superdeep (сверхглубокая) borehole intended to be 7,000 metres (23,000 ft) deep. Aralsor SG-1 and Biyikzhal SG-2 preceded the SG-3.


  1. ^ a b c Ault, Alicia (19 February 2015). "What's the deepest hole ever dug?". Ask Smithsonian. Smithsonian. Washington, DC: Smithsonian Institution.
  2. ^ "Sakhalin-1 project drills world's longest extended-reach well". Ordons News. BusinessWire. 29 January 2011. Archived from the original on 31 January 2011.
  3. ^ a b Королев, Владимир (6 August 2016). "Подземное неземное". nplus1.ru. Retrieved 8 August 2021.
  4. ^ "The KTB borehole – Germany's superdeep telescope into the Earth's crust" (PDF). Oilfield Review. January 1995. Archived from the original (PDF) on 19 December 2008. Retrieved 8 April 2009.
  5. ^ a b c d e Яковлев, Ю.Н.; Скуфьин, П.К.; Чвыков, О.С.Ч. (2014). "Влияние Природных Факторов на Траекторию и Форму Стволов Кольской Сверхглубокой Скважины (СГ-3)" (PDF). Вестник Кольского научного центра РАН (in Russian). Vol. 2014–03. pp. 8–15.
  6. ^ a b Osadchy, A. (2002). "Legendary Kola Superdeep". Наука и жизнь [Journal of Science and Life] (in Russian). Retrieved 8 May 2009.
  7. ^ "Why Is China Drilling a 33,000-Feet Hole in Xinjiang?". Time. 1 June 2023. Retrieved 16 August 2023.
  8. ^ "Kola Superdeep is in the Guinness Book of World Records". Zemlya I Vselennaya (in Russian). No. 3. 1989. p. 9.
  9. ^ Cassino, Adam (2003). "Depth of the deepest drilling". hypertextbook.com. The Physics Factbook.
  10. ^ a b Khokhlova, Galina (15 October 2008). "Гордость пойдет в утиль: Кольская сверхглубокая скважина будет ликвидирована" [Pride goes to waste: Kola superdeep borehole to be scrapped]. Российская Газета [Rossiyskaya Gazeta] (in Russian). Retrieved 9 July 2010.
  11. ^ Ramberg, I.B.; Bryhni, I. & Nøttvedt, A. (2008). The Making of a Land: Geology of Norway. Geological Society. p. 624. ISBN 978-82-92394-42-7. Retrieved 27 January 2010.
  12. ^ a b c Andrei, Mihai (3 June 2014). "The World's Deepest Hole Lies Beneath this Rusty Metal Cap - The Kola Superdeep Borehole". ZME Science. Retrieved 28 December 2022.
  13. ^ "95/01953 Characterization of crystalline rocks in deep boreholes. The Kola, Krivoy Rog and Tyrnauz boreholes". Fuel and Energy Abstracts. 36 (2): 133. March 1995. doi:10.1016/0140-6701(95)93618-1. ISSN 0140-6701.
  14. ^ "Where is Earth's Water? | U.S. Geological Survey". www.usgs.gov. Retrieved 28 December 2022.
  15. ^ Bellows, Alan (5 March 2007). "The Deepest Hole". Damn Interesting. Retrieved 27 December 2014.
  16. ^ "95/01953 Characterization of crystalline rocks in deep boreholes. The Kola, Krivoy Rog and Tyrnauz boreholes". Fuel and Energy Abstracts. 36 (2): 133. March 1995. doi:10.1016/0140-6701(95)93618-1. ISSN 0140-6701.
  17. ^ G. J. MacDonald (1988). "Major Questions About Deep Continental Structures". In A. Bodén and K. G. Eriksson (ed.). Deep drilling in crystalline bedrock, v. 1. Berlin: Springer-Verlag. pp. 28–48. ISBN 978-3-540-18995-4.
  18. ^ Smythe, D.K.; Smithson, S.B.; Humphreys, C.; Gillen, C.; Kristoffersen, Y.; Karaev, N.A.; Garipov, V.Z.; Pavlenkova, N.I. (1994). "Project images crust, collects seismic data in world's largest borehole" (PDF). Eos, Transactions American Geophysical Union. 75 (41): 473–476. doi:10.1029/94EO01089. ISSN 2324-9250.
  19. ^ Smythe, D.K. (videographer) (1992). Crustal seismic reflection profiling through the Kola superdeep well, Russia (video) – via YouTube.
  20. ^ "Росимущество ликвидирует самую глубокую скважину в мире". lenta.ru (in Russian). 10 April 2008. Retrieved 8 August 2021.
  21. ^ "Kola superdeep borehole, Murmansk, Russia". Atlas Obscura. Retrieved 14 August 2020.
  22. ^ Emmermann, Rolf; Lauterjung, Jörn (1997). "The German continental deep drilling program KTB: Overview and major results" (PDF). Journal of Geophysical Research: Solid Earth. 102 (B8): 18179–18201. Bibcode:1997JGR...10218179E. doi:10.1029/96JB03945. ISSN 2156-2202. Archived from the original (PDF) on 30 October 2012.
  23. ^ Cheung, Rachel (6 June 2023). "China begins drilling one of world's deepest holes in hunt for discoveries deep inside the Earth". the Guardian. Retrieved 10 June 2023. China has begun digging its deepest borehole in an effort to study areas of the planet deep beneath the surface. The drilling of the borehole began on Tuesday in a desert in the Tarim basin in China's north-western region of Xinjiang, according to the Chinese state-run Xinhua news agency. With a planned depth of 11,100 metres, the narrow shaft will penetrate more than 10 continental strata and reach the cretaceous system in the Earth's crust – a series of stratified rocks dating back 145 million years.
  24. ^ Sharma, Sejal (31 May 2023). "China's 10,000-meter deep dive into scientific exploration". interestingengineering.com. Retrieved 10 June 2023.
  25. ^ Sky News (2 June 2023). "China drilling hole over 11,000m deep into the desert". Sky News. Retrieved 10 June 2023.
  26. ^ Albert Andeso (11 March 2024). "China's Deepest Borehole Exceeds 10km Milestone". Construction Kenya. Retrieved 11 March 2024.
  27. ^ "Transocean GSF rig 127 drills deepest extended-reach well" (Press release). Transocean Ltd. 21 May 2008. Archived from the original on 12 November 2010. Retrieved 15 November 2010.
  28. ^ "Maersk Oil finished Drilling (BD-04A) well at Al-Shaheen field, Qatar". Gulf Oil & Gas Marketplace. 23 May 2008. Retrieved 15 November 2010.
  29. ^ "Kola Superdeep Borehole (KSDB)". ICDP. Archived from the original on 7 May 2014. Retrieved 21 July 2017.

Further reading[edit]

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