Kola Superdeep Borehole

Kola Superdeep Borehole
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