Kola Superdeep Borehole

Not to be confused with Mir mine, a large open-pit diamond mine in Russia.

Kola Superdeep Borehole, 2007

The Kola Superdeep Borehole (Russian: Кольская сверхглубокая скважина, Kolskaya sverkhglubokaya skvazhina) is the result of a scientific drilling project of the Soviet Union in the Pechengsky District, on the Kola Peninsula, longitude and latitude coordinate: . 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-metre-long (40,230 ft) in 1989 and still is the deepest artificial point on Earth.

In terms of true 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 surpassed in 2008 by the 12,289-metre-long (40,318 ft) Al Shaheen oil well in Qatar, and in 2011 by 12,345-metre-long (40,502 ft) Sakhalin-I Odoptu OP-11 Well (offshore the Russian island Sakhalin).

Drilling

Kola Superdeep Borehole, commemorated on the 1987 USSR stamp

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. 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 infeasible and the drilling was stopped in 1992. With the projected further increase in temperature with increasing depth, drilling to 15,000 m (49,000 ft) would have meant working at a temperature of 300 °C (570 °F), where the drill bit would no longer work.

Research

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.

Another unexpected discovery was a large quantity of hydrogen gas; the mud that flowed out of the hole was described as "boiling" with hydrogen.

Status

Kola Superdeep Borehole, 2012

The borehole itself (welded shut), August 2012

The project was closed down in late 2006 because of a lack of funding. All the drilling and research equipment was scrapped. 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 a lack of funding. This failure 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 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 specifically for KTB.

Records

The Kola Superdeep Borehole was the longest and deepest 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.

On 27 August 2012, Exxon Neftegas Ltd beat its own record by completing Z-44 Chayvo well. This ERD well reached a measured total depth of 12,376 meters (40,604 ft).

In terms of depth below the surface, the Kola Superdeep Borehole retains the world record.

See also

• Chikyū, deep oceanic drilling ship, which achieved a subsea drilling record in 2012.
• Earthscope
• Extreme points of Earth
• Lake Vostok
• Mohorovičić discontinuity
• San Andreas Fault Observatory at Depth
• USARRAY
• The Well to Hell hoax

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 (Russian)