1. Drilling

2. Research

3. Status

4. Similar projects

5. Records

6. See also

7. References

8. Further reading

9. External links

The Kola Superdeep Borehole ({{lang-ru|link=no|Кольская сверхглубокая скважина|tr=Kolskaya sverkhglubokaya skvazhina}}) 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 {{convert|12,262|m|ft mi}} in 1989 and is the deepest artificial point on Earth, {{asof|2019|03|lc=y}}. The borehole is {{convert|9|in|cm|order=flip}} in diameter.^[1]

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 {{convert|12289|m|ft|adj=mid|-long}} Al Shaheen oil well in Qatar, and in 2011 by the {{convert|12345|m|ft|adj=mid|-long}} Sakhalin-I Odoptu OP-11 Well (offshore from the Russian island of Sakhalin).^[2]

Drilling

The main target depth was set at {{convert|15000|m|abbr=on}}. On 6 June 1979, the world depth record held by the Bertha Rogers hole in Washita County, Oklahoma, United States, at {{convert|9583|m|abbr=on}}^[2] was broken. In 1983, the drill passed {{convert|12000|m|abbr=on}}, and drilling was stopped for about a year for numerous scientific and celebratory visits to the site.^[4] This idle period may have contributed to a breakdown on 27 September 1984: after drilling to {{convert|12066|m|abbr=on}}, a {{convert|5000|m|abbr=on}} section of the drill string twisted off and was left in the hole. Drilling was later restarted from {{convert|7000|m|abbr=on}}.^[3]

The hole reached {{convert|12262|m|abbr=on}} in 1989. In that year, the hole depth was expected to reach {{convert|13500|m|abbr=on}} by the end of 1990 and {{convert|15000|m|abbr=on}} by 1993.^[4][5] Because of higher-than-expected temperatures at this depth and location, {{convert|180|°C|°F|0}} instead of the expected {{convert|100|°C|°F|0}}, drilling deeper was deemed unfeasible and the drilling was stopped in 1992.^[3]

Research

The Kola borehole penetrated about a third of the way through the Baltic Shield continental crust, estimated to be around {{convert|35|km|mi|0}} deep, reaching Archaean rocks at the bottom.^[6] 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 {{Convert|7|km|abbr=on}}, 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.^[7]

Microscopic plankton fossils were found 6 kilometers (4 mi) below the surface.^[1]

Another unexpected discovery was a large quantity of hydrogen gas. The mud that flowed out of the hole was described as "boiling" with hydrogen.^[8]

Status

The project ended in 1995 due to the dissolution of the Soviet Union and the site has since been abandoned.^[9] The ruins of the site, however, are frequently visited by curious sightseers.

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. 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 {{convert|9101|m|ft|abbr=on}} reaching temperatures of more than {{convert|260|°C|°F}}. Its ambitious measuring program used high-temperature logging tools that were upgraded specifically for KTB.^[10]

Records

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 {{convert|12289|m|abbr=on}}, with a record horizontal reach of {{convert|10902|m|abbr=on}} in only 36 days.^[11][12]

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 {{convert|12345|m|abbr=on}} and a horizontal displacement of {{convert|11475|m|abbr=on}}. Exxon Neftegas completed the well in 60 days.^[13]

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 {{convert|12376|m|}}.^[14]

In terms of depth below the surface, the Kola Superdeep Borehole SG-3 retains the world record at {{convert|12,262|m}} in 1989 and is still the deepest artificial point on Earth.^[15]

See also

• {{annotated link|Chikyū}}, deep oceanic drilling ship, which achieved a subsea drilling record in 2012.
• {{annotated link|Earthscope}}
• {{annotated link|Extreme points of Earth}}
• {{annotated link|Lake Vostok}}
• {{annotated link|List of deepest mines}}
• {{annotated link|Mohorovičić discontinuity}}
• {{annotated link|San Andreas Fault Observatory at Depth}}
• {{annotated link|USArray}}
• {{annotated link|Well to Hell hoax}} observed since 1995

References

Further reading

• {{cite book| last = Fuchs| first = K.| author2 = Kozlovsky, E.A. | author3 = Krivtsov, A.I. | author4=Zoback, M.D. | lastauthoramp=yes | title = Super-Deep Continental Drilling and Deep Geophysical Sounding| date = 1990| publisher = Springer Verlag| location = Berlin| isbn = 978-0-387-51609-7| page = 436 }}
• {{cite book| last = Kozlovsky| first = Ye.A| title = The Superdeep Well of the Kola Peninsula| date = 1987| publisher = Springer Verlag| location = Berlin| isbn = 978-3-540-16416-6| page = 558 }}

External links

• Official Kola Superdeep Borehole website (in Russian)
• The World's Deepest Hole – Alaska Science Forum – July 1985
• The Deepest Hole 20 June 2006
• Kola Superdeep – Scientific research results and experiences by PhD A. Osadchikh 1984 {{Ru icon}}

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