Kola Superdeep Borehole

The Kola Superdeep Borehole SG-3 (Russian: Кольская сверхглубокая скважина СГ-3, romanizedKol'skaya sverkhglubokaya skvazhina SG-3) is the deepest human-made hole on Earth, which attained maximum true vertical depth of 12,262 metres (40,230 ft; 7.619 mi) in 1989.[1] It is the result of a scientific drilling effort to penetrate as deep as possible into the Earth's crust conducted by the Soviet Union in the Pechengsky District of the Kola Peninsula, near the Russian border with Norway.

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
  • 1994

SG (СГ) is a Russian designation for a set of superdeep (Russian: сверхглубокая) boreholes conceived as part of a Soviet scientific research programme of the 1960s, 1970s and 1980s. Aralsor SG-1 (in the Pre-Caspian Basin of west Kazakhstan) and Biyikzhal SG-2 (in Krasnodar Krai), both less than 6,810 metres (22,340 ft) deep, preceded Kola SG-3, which was originally intended to reach 7,000 metres (23,000 ft) deep.[2] Drilling at Kola SG-3 began in 1970 using the Uralmash-4E, and later the Uralmash-15000 series drilling rig. A total of five 23-centimetre-diameter (9 in) boreholes were drilled, two branching from a central shaft and two off of one of those branches.

In addition to being the deepest human-made hole on Earth, Kola Superdeep Borehole SG-3 was, for almost three decades, the world's longest borehole in measured depth along its bore, until surpassed in 2008 by a hydrocarbon extraction borehole in Qatar.[3]


Kola Superdeep Borehole, commemorated on a 1987 USSR stamp

Drilling at Kola SG-3 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).[4]

On 6 June 1979, the world depth record then held by the Bertha Rogers hole in Washita County, Oklahoma, United States, at 9,583 metres (31,440 ft),[5] was broken by Kola SG-3. In October 1982, Kola SG-3's first hole reached 11,662 metres (38,261 ft).[6]

The second hole was started in January 1983 from a 9,300-metre (30,500 ft) depth of the first hole.[4] 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.[7] 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.[7][6]

The third hole reached 12,262 metres (40,230 ft) in 1989.[8] 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.[9][10][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.[6][11]



The stated areas of study of the Kola Superdeep Borehole 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. Drilling penetrated about a third of the way through the Baltic Shield of the continental crust, estimated to be around 35 kilometres (22 mi) deep, reaching Archean rocks at the bottom.[12] Numerous unexpected geophysical discoveries were made:

  • During the drilling process, the expected basaltic layers at 7 kilometres (4.3 mi) down were never found, nor were basaltic layers at any depth.[13] There were instead more granites, deeper than predicted. The prediction of a transition at 7 kilometres (4.3 mi) 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.[13]
  • Water pooled 3–6 kilometres (1.9–3.7 mi) below the surface,[13][14] having percolated up through the granite until it reached a layer of impermeable rock.[15][16] This water did not naturally vaporize at any depth in the borehole.[17]
  • Microscopic plankton fossils were found 6 kilometres (3.7 mi) below the surface.[1]

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.[19] The experiment was documented in a video recorded by Professor David Smythe,[20] 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.[11] 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.[6] In 2007, the scientific team was dissolved and the equipment was transferred to a private company and partially liquidated.[6]

In 2008, the company was liquidated due to unprofitability,[21] 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.[22]

Similar projects




The 12,262 m (40,230 ft) deep Kola Superdeep Borehole has been the world's deepest borehole since 1979.[1][28] It was also the longest borehole in the world from 1979 to 2008. Its record length was surpassed in May 2008 by the curved extended reach drilling bore of well BD-04A in the Al Shaheen Oil Field in Qatar, which attained a total length of 12,289 metres (40,318 ft) but depth of just 1,387 metres (4,551 ft).[29][30]

See also



  1. ^ a b c Ault, Alicia (19 February 2015). "What's the deepest hole ever dug?". Ask Smithsonian. Smithsonian. Washington, DC: Smithsonian Institution.
  2. ^ Alekseyev, F.A.; Kukharenko, N.K.; Voytov, G.I.; Galkin, Yu.A. (1972). "Initial results of geophysical and geochemical investigations of very deep boreholes". International Geology Review. 14 (3): 275–280. doi:10.1080/00206817209475693.
  3. ^ "Sakhalin-1 project drills world's longest extended-reach well". Ordons News. BusinessWire. 29 January 2011. Archived from the original on 31 January 2011.
  4. ^ a b Королев, Владимир (6 August 2016). "Подземное неземное". nplus1.ru. Retrieved 8 August 2021.
  5. ^ "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.
  6. ^ 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.
  7. ^ a b Osadchy, A. (2002). "Legendary Kola Superdeep". Наука и жизнь [Journal of Science and Life] (in Russian). Retrieved 8 May 2009.
  8. ^ "Why Is China Drilling a 33,000-Feet Hole in Xinjiang?". Time. 1 June 2023. Retrieved 16 August 2023.
  9. ^ "Kola Superdeep is in the Guinness Book of World Records". Zemlya I Vselennaya (in Russian). No. 3. 1989. p. 9.
  10. ^ Cassino, Adam (2003). "Depth of the deepest drilling". hypertextbook.com. The Physics Factbook.
  11. ^ 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.
  12. ^ 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.
  13. ^ 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.
  14. ^ "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.
  15. ^ "Where is Earth's Water? | U.S. Geological Survey". www.usgs.gov. Retrieved 28 December 2022.
  16. ^ Bellows, Alan (5 March 2007). "The Deepest Hole". Damn Interesting. Retrieved 27 December 2014.
  17. ^ "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.
  18. ^ 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.
  19. ^ 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.
  20. ^ Smythe, D.K. (videographer) (1992). Crustal seismic reflection profiling through the Kola superdeep well, Russia (video) – via YouTube.
  21. ^ "Росимущество ликвидирует самую глубокую скважину в мире". lenta.ru (in Russian). 10 April 2008. Retrieved 8 August 2021.
  22. ^ "Kola superdeep borehole, Murmansk, Russia". Atlas Obscura. Retrieved 14 August 2020.
  23. ^ 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.
  24. ^ 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.
  25. ^ Sharma, Sejal (31 May 2023). "China's 10,000-meter deep dive into scientific exploration". interestingengineering.com. Retrieved 10 June 2023.
  26. ^ Sky News (2 June 2023). "China drilling hole over 11,000m deep into the desert". Sky News. Retrieved 10 June 2023.
  27. ^ Albert Andeso (11 March 2024). "China's Deepest Borehole Exceeds 10km Milestone". Construction Kenya. Retrieved 11 March 2024.
  28. ^ "Kola Superdeep Borehole (KSDB)". ICDP. Archived from the original on 7 May 2014. Retrieved 21 July 2017.
  29. ^ "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.
  30. ^ "Maersk Oil finished Drilling (BD-04A) well at Al-Shaheen field, Qatar". Gulf Oil & Gas Marketplace. 23 May 2008. Retrieved 15 November 2010.

Further reading

  • Fuchs, K.; Kozlovsky, E.A.; Krivtsov, A.I. & Zoback, M.D. (1990). Super-Deep Continental Drilling and Deep Geophysical Sounding. Berlin: Springer Verlag. p. 436. ISBN 978-0-387-51609-7.
  • Kozlovsky, Ye.A (1987). The Superdeep Well of the Kola Peninsula. Berlin: Springer Verlag. ISBN 978-3-540-16416-6.