Kola Superdeep Borehole

The Kola Superdeep Borehole (Russian: Кольская сверхглубокая скважина, romanizedKol'skaya sverkhglubokaya skvazhina) SG-3[note 1] 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 deeply as possible into the Earth's crust.

Kola Superdeep Borehole
Кольская сверхглубокая скважина crop.jpg
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; 30.6100Coordinates: 69°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

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 (9 in) diameter 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 artificial point on Earth.

In terms of true vertical depth, it is 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 until it was surpassed in 2008 by the 12,289-metre-long (40,318 ft) Al Shaheen Oil Well in Qatar.[2][citation needed]


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-meter (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 meters (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 5,000-millimetre (200 in) section of the drill string twisted off and was left in the hole. Drilling was restarted in September 1986 from 7,000 metres (23,000 ft) from the first hole.[6][5]

The third hole reached 12,262 metres (40,230 ft) in 1989.[citation needed] 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.[7][8][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][9]

Because of higher-than-expected temperatures at this depth and location, 180 °C (356 °F) instead of the expected 100 °C (212 °F), drilling deeper was deemed unfeasible. The unexpected decrease in density, the greater porosity, and the unexpectedly high temperatures caused the rock to behave somewhat like a plastic, making drilling nearly impossible.[10][better source needed]


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.

To scientists, one of the more fascinating findings to emerge from this well is that no transition from granite to basalt was found at the depth of about seven kilometres (4.3 mi), where the velocity of seismic waves has a discontinuity. Instead, the change in the seismic wave velocity is caused by a metamorphic transition in the granite rock. In addition, the rock at that depth had been thoroughly fractured and was saturated with water, which was surprising. This water, unlike surface water, must have come from deep-crust minerals and had been unable to reach the surface because of a layer of impermeable rock.[12]

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.[13]

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 Scotland, the University of Wyoming in the United States, and the University of Bergen in Norway, as well as several Russian earth science research institutions.[14] The experiment was documented in a video recorded by Professor David Smythe,[15] which shows the drilling deck in action during an attempt to recover a tool dropped down the hole.


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

The drilling terminated in 1995 due to a lack of funds.[9] The scientific team was transferred to the federal state unitary subsidiary enterprise "Kola Superdeep", reduced and reoriented to a thorough study of 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,[16] and the site was abandoned. The site is still visited by curious sightseers, who have reported that the structure over the borehole has been partially destroyed or removed.[10]

Similar projectsEdit


The Kola Superdeep Borehole was the longest and deepest borehole in the world from 1989 to 2008.[citation needed]

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).[18][19]

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.[20]

See alsoEdit


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


  1. ^ a b "Ask Smithsonian: What's the Deepest Hole Ever Dug?", smithsonian.com, 19 February 2015
  2. ^ Sakhalin-1 Project Drills World's Longest Extended-Reach Well Archived 31 January 2011 at the Wayback Machine
  3. ^ a b Королев, Владимир. "Подземное неземное". nplus1.ru. Retrieved 8 August 2021.
  4. ^ "The KTB Borehole—Germany's Superdeep Telescope into the Earth's Crust" (PDF). Oilfield Review. 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. 2014–3: 8–15.
  6. ^ a b A. Osadchy (2002). "Legendary Kola Superdeep". Наука и жизнь (Journal of Science and Life) (in Russian). Retrieved 8 May 2009.
  7. ^ Kola Superdeep is in the Guinness Book of World Records, Zemlya i Vselennaya, 1989, no. 3, p.9 (in Russian)
  8. ^ Cassino, Adam (2003). "Depth of the Deepest Drilling". The Physics Factbook.
  9. ^ a b Galina Khokhlova (15 October 2008). "Гордость пойдет в утиль: Кольская сверхглубокая скважина будет ликвидирована (Pride goes to waste: Kola superdeep borehole to be scrapped)" (in Russian). Российская Газета (Rossiyskaya Gazeta). Retrieved 9 July 2010.
  10. ^ a b [1] Kola Superdeep Borehole, Murmansk, Russia (Atlas Obscura, accessed 14 August 2020)
  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. ^ Alan Bellows (5 March 2007). "The Deepest Hole". Damn Interesting. Retrieved 27 December 2014.
  13. ^ 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.
  14. ^ 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.
  15. ^ [2] Smythe, D. K. (1992). Crustal seismic reflection profiling through the Kola superdeep well, Russia.
  16. ^ "Росимущество ликвидирует самую глубокую скважину в мире". lenta.ru. Retrieved 8 August 2021.
  17. ^ 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.
  18. ^ "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.
  19. ^ "Maersk Oil finished Drilling (BD-04A) well at Al-Shaheen field, Qatar". Gulf Oil & Gas Marketplace. 23 May 2008. Retrieved 15 November 2010.
  20. ^ "Kola Superdeep Borehole (KSDB)". ICDP. Archived from the original on 7 May 2014. Retrieved 21 July 2017.

Further readingEdit

External linksEdit