The Kola Superdeep Borehole () SG-3
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 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, and it became the deepest manmade hole in history in 1979. The  diameter boreholes were drilled by branching from a central hole. The deepest reached  in 1989, the deepest human-made hole on Earth, and remains so .
 
In terms of true vertical depth, it remains 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 (that is, borehole length) until it was surpassed in 2008 by the  long Al Shaheen Oil Well in Qatar.

Drilling

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  depth. In 1974, the new purpose-built Uralmash-15000 drilling rig was installed onsite, named after the new target depth, set at .

On 6 June 1979, the world depth record held by the Bertha Rogers hole in Washita County, Oklahoma, United States, at , was broken. In October 1982, the first hole reached , and the second hole was started in January 1983 from a  depth of the first hole.

In 1983, the drill passed  in the second hole, 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 after drilling resumed; on 27 September 1984, after drilling to , a  section of the drill string twisted off and was left in the hole. Drilling was restarted in September 1986,  from the first hole.

The third hole reached  in 1989. In that year, the hole depth was expected to reach  by the end of 1990 and  by 1993.

In June 1990, a breakdown occurred in the third hole at  of depth. The drilling of the fourth hole was started in January 1991 from  of depth of third hole. The drilling of the fourth hole was stopped in April 1992 at  of depth. Drilling of the fifth hole started in April 1994 from  of depth of the third hole. Drilling was stopped in August 1994 at  of depth due to lack of funds and the well itself was mothballed.

During the drilling process, unexpectedly no basaltic layers were found at seven kilometers down or at any depth in the borehole.  Prior to that, geological information about the earth's crust was mostly based on analyzing seismic waves that indicated discontinuity.  Scientific models had previously suggested basalt should be seen.  Instead, the actual geological evidence from the borehole revealed there were more granites, and at much greater depths than scientists had considered.  It was then thought by scientists that seismic discontinuity was caused by granite metamorphosis instead of basalts. In addition to this, water was unexpectedly found at three to six kilometers deep.  Water was not naturally vaporizing at any depth in the borehole. Instead, water was found at these greater depths. Scientific models previously had not predicted water to be found at such great depths.  It was discovered that deep granites can be fractured and receive water this deep. As a result of these findings, many scientists now theorize that aquifers of water can be found at much greater depths than older scientific models had previously thought possible.

Research
The Kola Superdeep Borehole penetrated about a third of the way through the Baltic Shield continental crust, estimated to be around  deep, reaching Archean rocks at the bottom. 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 , 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.

Microscopic plankton fossils were found  below the surface.

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.

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.
The experiment was documented in a video recorded by Professor David Smythe,
which shows the drilling deck in action during an attempt to recover a tool dropped down the hole.

Status

The drilling terminated in 1995 due to a lack of funds. 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. In 2007, the scientific team was dissolved and the equipment was transferred to a private company and partially liquidated.

In 2008, the company was liquidated due to unprofitability, 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.

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 of Mexico. After initial drilling, the project was abandoned in 1966 when funding was cut off. This program inspired 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 , reaching temperatures of more than . Its ambitious measuring program used high-temperature logging tools that were upgraded specifically for KTB.
 In 2023, China embarked on a 10,000 m super-deep borehole in the Tarim Basin in the Xinjiang region for scientific, oil and gas exploration.

Records
The Kola Superdeep Borehole was both the longest and deepest borehole in the world from 1989 to 2008. 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  and a horizontal reach of . In terms of depth below the surface, the Kola Superdeep Borehole SG-3 retains the world record at  reached in 1989 and is still the deepest artificial point on Earth.

See also
 , deep oceanic drilling ship, which achieved a subsea drilling record in 2012
 , covers the lowest point on land
 
 
 
 
 
 
 
 Vertical seismic profile — relevant seismic measurements
  - observed since 1995

Notes

References

Further reading

External links

 Official Kola Superdeep Borehole website 
 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 
 Photo report on a trip to the Kola superdeep well in 2017. Many photos of the current state. 

Structure of the Earth
Buildings and structures in Murmansk Oblast
Science and technology in Russia
Science and technology in the Soviet Union
Deepest boreholes
1970 establishments in the Soviet Union
Cancelled projects
Earth's crust
콜라 초심층 시추공()은 소련 콜라반도의 페첸스키구에서 진행된 과학 시추 프로젝트의 일환으로 굴착된 시추공이다. 이 프로젝트는 지구의 지각을 최대한 깊게 파보는 프로젝트였다. 1970년 5월 24일 굴착 장비인 Uralmash-4E를, 나중에는 Uralmash-15000 계열 장비를 이용하여 파내기 시작했다. 중앙 시추공을 원점으로 여러 시추공을 뚫는 방식이었는데, 가장 깊이 들어간 SG-3 구멍은 1989년 12,262m에 도달하여 현재까지 가장 깊이 들어간 구멍 중 하나로 계속 남아 있다.

순수 깊이만으로는 콜라 시추공이 지구상에서 가장 깊이 뚫린 구멍이다. 근 20년 동안에는 측정 깊이로도 세계에서 가장 깊은 시추공 중 하나였으나, 2008년 카타르에서 알샤헨 유정이 12,289m를 뚫고, 2011년 러시아의 사할린섬에서 사할린-I Odoptu OP-11 시추공이 12,345m 깊이의 구멍을 뚫으면서 이 기록은 깨지게 되었다.

시추 

주요 목표 깊이는 15,000m였다. 1979년 6월 6일, 당시까지 최고 깊이였던 미국 오클라호마주 워시타 군 버샤 로저 구멍의 기록을 돌파했으며 1983년, 12,000m 지점을 통과하며 다수의 축하 방문 및 여러 연구로 시추가 1년간 중단되었다. 이후 1984년 9월 27일에는 시추 장비가 고장나면서 작업이 다시 한 번 중단되었다. 12,066m를 시추한 후에는 5,000m 지점의 드릴 스트링이 비틀려 끊어지고 구멍 안에 방치되었다. 이후 7,000m 지점에서 다시 시추를 시작했다.

1989년에는 12,262m에 도달했으며 1990년 말까지 13,500m, 1993년에는 15,000m에 도달할 것이라고 예측됐다. 그러나, 온도가 예상했던 100 °C보다 높은 180 °C에 달해 추가 시추가 불가능할 것으로 판단하고 1992년 중단되었다.

연구 
콜라 시추공은 35km 깊이로 추정되는 페노스칸디아 대륙 지각의 3분의 1을 시추하여 가장 아랫부분의 바위는 25억년 나이의 시생누대 시기까지 도달했다. 이 프로젝트는 광범위한 지구물리학 연구에 사용되었다. 이 연구에서 언급된 영역은 페노스칸디아 지역의 심층 구조, 지구 지각의 지진학적 불연속면 및 열체제, 깊은 지각의 물리화학적 조성과 지각 상부에서 하부로의 전이 과정, 암석권의 지구물리학적 연구, 깊은 깊이의 지구물리학 연구 기술의 개발과 발전 등이 있었다.

과학자들에게 가장 매혹적이었던 연구 결과로는 지진파의 불연속(모호로비치치 불연속면)이 나타나는 7km 지점에서 암석 물성이 화강암에서 현무암으로 바뀌지 않는다는 것이었고, 불연속은 화강암의 변성암으로의 변이로 일어난다는 것이 밝혀졌다. 또한, 그 깊이에서 암석은 완전히 파쇄되었고 물로 엄청나게 포화된 상태였다. 지상에서의 물과 달리 이 물은 깊은 지각의 광물로부터 왔으며 불투과성 암석층 때문에 표면까지 올라올 수 없었다.

또 다른 예기치 않은 발견은 대량의 수소 발견이었다. 시추공에서 흘러나온 진흙은 수소로 끓어오르는 모습이었다고 전해진다.

상태 

재정난으로 인해 2005년 폐쇄되었다. 모든 시추 및 연구 장비는 폐기되었고, 2008년 이후로는 방치되었다.

비슷한 프로젝트 
 미국은 1957년 모홀 프로젝트라는 이름의 멕시코 지역의 태평양 연안에서 얕은 지각을 관통한다는 계획을 시작했다. 그러나, 시추 초기에 이 프로젝트는 자금난으로 1966년 폐기되었다. 이 실패는 이후 심해굴착계획, 해양 굴착 계획, 현재의 통합 해양 굴착 프로그램의 성공으로 이어지게 되는 계기가 되었다.
 바이에른주 북부 빈디셰스셰첸베흐(Windischeschenbach)의 KTB 초깊이 시추공(독일 대륙 초깊이 시추 프로그램, 1990년~1994년)은 9,101m까지 파내려가고 그 곳에서 260 °C 온도에 도달했다. 이 야심찬 측정 프로그램에는 KTB 시추공을 위해 특별히 업그레이드한 고온 측정 장비를 이용했다.

기록 
콜라 시추공은 1989년 이후로 거의 20년 동안 가장 길고 가장 깊은 시추공이었다. 그러나 2008년 5월 카타르 알샤헨 유정의 BD-04A 시추공이 36일만에 총 깊이 12,289m, 횡축 이동 10,092m를 달성하며 가장 긴 시추공 기록을 갱신했다.

2011년 1월 28일, 사할린-I 프로젝트를 진행하는 엑슨 네프트가스가 사할린섬에서 Odopu OP-11 시추공으로 알샤헨 시추공을 뛰어넘어 기록을 다시 갱신했다. Odoptu OP-11 시추공은 총 깊이 12,345m, 횡축 이동 11,475m이며 60일만에 완공되었다.

지표면 기준 가장 깊은 깊이를 판 시추공으로는 콜라 시추공이 아직 지위를 유지하고 있다.

더 보기 
 지큐 - 2012년 이후로 최대 깊이 해저 시추 기록을 달성한 해양 시추선
 모호로비치치 불연속면

각주

참고 문헌

외부 링크 

  콜라 시추공 공식 홈페이지
 The World's Deepest Hole – Alaska Science Forum – July 1985
 The Deepest Hole (2006년 6월 20일)
  Kola Superdeep - Scientific research results and experiences by PhD A. Osadchikh (1984년)

지구의 구조
러시아의 과학과 기술
소련의 과학과 기술
무르만스크주의 건축물
시추공
지구의 지각