Kola Superdeep Borehole
The Kola Superdeep Borehole (Russian: Кольская сверхглубокая скважина, Kolskaya sverkhglubokaya skvazhina) is the result of a scientific drilling project of the Soviet Union 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. A number of boreholes were drilled by branching from a central hole. The deepest, SG-3, reached 12,262 metres (40,230 ft) (2.21 leagues) in 1989, and is the deepest hole ever drilled, and the deepest artificial point on Earth. For two decades it was also the world's longest borehole, in terms of measured depth along the well bore, until surpassed in 2008 by the 12,289 m (40,318 ft) long Al Shaheen oil well in Qatar, and in 2011 by 12,345 m (40,502 ft) long Sakhalin-I Odoptu OP-11 Well (offshore the Russian island Sakhalin).
The main target depth was set at 15,000 m (49,000 ft). On 6 June 1979, the world depth record held by the Bertha Rogers hole in Washita County, Oklahoma, at 9,583 m (31,440 ft) was broken. In 1983, the drill passed 12,000 m (39,000 ft), and drilling was stopped for about a year to celebrate the event. This idle period may have contributed to a breakdown on 27 September 1984: after drilling to 12,066 m (39,587 ft), a 5,000 m (16,000 ft) section of the drill string twisted off and was left in the hole. Drilling was later restarted from 7,000 m (23,000 ft). The hole reached 12,262 m (40,230 ft) in 1989. In that year the hole depth was expected to reach 13,500 m (44,300 ft) by the end of 1990 and 15,000 m (49,000 ft) by 1993. However, because of higher-than-expected temperatures at this depth and location, 180 °C (356 °F) instead of expected 100 °C (212 °F), drilling deeper was deemed unfeasible and the drilling was stopped in 1992. With the expected further increase in temperature with increasing depth, drilling to 15,000 m (49,000 ft) would have meant working at a projected 300 °C (570 °F), at which the drill bit would no longer work.
The Kola borehole penetrated about a third of the way through the Baltic continental crust, estimated to be around 35 kilometres (22 mi) deep, reaching rocks of Archaean age (greater than 2.5 billion years old) at the bottom. The project has been a site of extensive geophysical studies. 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 7 km, 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.
The project was closed down in late 2005 because of lack of funding. All the drilling and research equipment was scrapped and the site has been abandoned since 2008.
Similar projects 
- The United States had embarked on a similar project in 1957, dubbed Project Mohole, which was intended to penetrate the shallow crust under the Pacific Ocean off Mexico. However, after some initial drilling, the project was abandoned in 1966 because of lack of funding. This failure inspired the great successes of the Deep Sea Drilling Project, Ocean Drilling Program and the present Integrated Ocean Drilling Program.
- The KTB superdeep borehole (German Continental Deep Drilling Program, 1990–1994) at Windischeschenbach in northern Bavaria was drilled down to a depth of 9,101 m (29,859 ft) reaching temperatures of more than 260 °C (500 °F). Its ambitious measuring program used high-temperature logging tools that were upgraded especially for KTB.
Longest borehole record 
The deep core-drilled Kola borehole cannot be directly compared with any other borehole in the world. In a deep core borehole, a section of the rock drilled through is recovered from within the hole. It is this recovered drill core, and the information it represents about the rock that it was retrieved from, that is the most important feature of the borehole.
The Kola Superdeep Borehole was the deepest and longest borehole in the world for nearly 20 years. However, in May 2008, a new record for borehole length was established by the extended-reach drilling (ERD) well BD-04A, which was drilled by Transocean for Maersk Oil in the Al Shaheen oil field in Qatar. It was drilled to 12,289 m (40,318 ft), with a record horizontal reach of 10,902 m (35,768 ft), in only 36 days.
On 28 January 2011, Exxon Neftegas Ltd., operator of the Sakhalin-I project, drilled the world's longest extended-reach well offshore on the Russian island of Sakhalin. It has surpassed the length of both the Al Shaheen well and the Kola borehole. The Odoptu OP-11 well reached a measured total depth of 12,345 m (40,502 ft) and a horizontal displacement of 11,475 m (37,648 ft). Exxon Neftegas completed the well in 60 days.
However, in terms of depth below the surface, the Kola Superdeep Borehole still retains the world record as of May 2013.
See also 
- Chikyū, deep oceanic drilling ship, which achieved a subsea drilling record in 2012.
- Extreme points of Earth
- Mohorovičić discontinuity
- San Andreas Fault Observatory at Depth
- Well to Hell hoax
- "Kola Superdeep Borehole (KSDB)". ICDP. Archived from the original on 1 February 2010. Retrieved 8 April 2009.
- Sakhalin-1 Project Drills World's Longest Extended-Reach Well
- "The KTB Borehole—Germany's Superdeep Telescope into the Earth's Crust" (PDF). Oilfield Review. Retrieved 8 April 2009.
- A. Osadchy (no. 5, 2002). "Legendary Kola Superdeep". Наука и жизнь (Journal of Science and Life) (in Russian). Retrieved 8 April 2009.
- Kola Superdeep is in the Guinness Book of World Records, Zemlya i Vselennaya, 1989, no. 3, p.9 (Russian)
- Cassino, Adam (2003). "Depth of the Deepest Drilling". The Physics Factbook.
- 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.
- Alan Bellows (5 March 2007). "The Deepest Hole". Damn Interesting. Retrieved 8 April 2009.
- G.J. MacDonald (1988). "Major Questions About Deep Continental Structures". In A. Bodén and K.G. Eriksson. Deep drilling in crystalline bedrock, v. 1. Berlin: Springer-Verlag. pp. 28–48. ISBN 978-3-540-18995-4.
- Galina Khokhlova (15 October 2008). "From glory to disgrace" (in Russian). Retrieved 9 July 2010.
- "Transocean GSF Rig 127 Drills Deepest Extended-Reach Well" (Press release). Transocean Ltd. 21 May 2008. Retrieved 15 November 2010.
- "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., and 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. p. 558. ISBN 978-3-540-16416-6.
|Wikimedia Commons has media related to: Kola Superdeep Borehole|
- Official Kola Superdeep Borehole website (in Russian)
- The World's Deepest Hole – Alaska Science Forum – July 1985
- The Deepest Hole 20 June 2006