Kola Superdeep Borehole
Superstructure of the Kola Superdeep Borehole, 2007
|Greatest depth||12,262 metres (40,230 ft; 7.619 miles)|
The Kola Superdeep Borehole (Russian: Кольская сверхглубокая скважина) is the result of a scientific drilling project of the Soviet Union in the Pechengsky District, 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. Boreholes were drilled by branching from a central hole. The deepest, SG-3, reached 12,262 metres (40,230 ft) in 1989 and is still the deepest artificial point on Earth. The borehole is 23 centimetres (9 in) in diameter.
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, and in 2011 by the 12,345-metre-long (40,502 ft) Sakhalin-I Odoptu OP-11 Well (offshore from the Russian island of 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, United States, 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 for numerous scientific and celebratory visits to the site. 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. 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 and the drilling was stopped in 1992.
The Kola borehole penetrated about a third of the way through the Baltic Shield continental crust, estimated to be around 35 kilometres (22 mi) deep, reaching Archaean rocks 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 (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.
The project ended in 1995 due to the dissolution of the Soviet Union. The site has since been abandoned, and is now an environmental hazard. The ruins of the site, however, are frequently visited by curious sightseers.
- 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. After some initial drilling, the project was abandoned in 1966 because of a lack of funding. This program inspired the great successes of the Ocean Drilling Program, Integrated Ocean Drilling Program and the present International Ocean Discovery Program.
- The KTB superdeep borehole (German Continental Deep Drilling Programme, 1987-1995) at Windischeschenbach in northern Bavaria was drilled 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 specifically for KTB.
The Kola Superdeep Borehole was the longest and deepest borehole in the world for nearly 20 years. 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 length 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.
On 27 August 2012, Exxon Neftegas Ltd beat its own record by completing the Z-44 Chayvo well. This ERD well reached a measured total length of 12,376 metres (40,604 ft).
- "Kola Superdeep Borehole (KSDB)". ICDP. Archived from the original on 1 February 2010. Retrieved 8 April 2009.
- "Ask Smithsonian: What's the Deepest Hole Ever Dug?", smithsonian.com, 19 February 2015
- Sakhalin-1 Project Drills World's Longest Extended-Reach Well Archived 31 January 2011 at the Wayback Machine.
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- Alan Bellows (5 March 2007). "The Deepest Hole". Damn Interesting. Retrieved 27 December 2014.
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- 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.
- "Archived copy" (PDF). Archived from the original (PDF) on 30 October 2012. Retrieved 5 November 2013.
- "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.
- "Maersk Oil finished Drilling (BD-04A) well at Al-Shaheen field, Qatar". Gulf Oil & Gas Marketplace. 23 May 2008. Retrieved 15 November 2010.
- "Kola Superdeep Borehole (KSDB)". ICDP. Retrieved 21 July 2017.
- 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. p. 558. ISBN 978-3-540-16416-6.
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