THE DEEPEST HUMAN-MADE HOLE ON EARTH

Did you know that the Kola Superdeep Borehole was both the longest and deepest borehole in the world from 1989 to 2008, and still retains the world record at 12,262 metres (40,230 ft) making it the deepest artificial point on Earth?

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. 

According to some, it is the entrance to hell. Its 40,230ft-deep (12.2km) construction is so deep that locals swear you can hear the screams of souls tortured in hell. It took the Soviets almost 20 years to drill this far, but the drill bit was still only about one-third of the way through the crust to the Earth’s mantle when the project came grinding to a halt in the chaos of post-Soviet Russia.

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. On 6 June 1979, the world depth record held by the Bertha Rogers hole in Washita County, Oklahoma, United States, at 9,583 meters (31,440 ft), was broken. In October 1982, the first hole reached 11,662 metres (38,261 ft), and the second hole was started in January 1983 from a 9,300 metres (30,500 ft) depth of the first hole. In 1983, the drill passed 12,000 metres (39,000 ft) in the second hole, and drilling was stopped for about a year for numerous scientific and celebratory visits to the site.

On 27 September 1984, after drilling to 12,066 metres (39,587 ft), a 5,000 millimetres (200 in) section of the drill string twisted off and was left in the hole. Drilling was restarted in September 1986, 7,000 metres (23,000 ft) from the first hole. The third hole reached 12,262 metres (40,230 ft) in 1989. In that year, the hole depth was expected to reach 13,500 metres (44,300 ft) by the end of 1990 and 15,000 metres (49,000 ft) by 1993.

In June 1990, a breakdown occurred in the third hole at 12,262 metres (40,230 ft) of depth. The drilling of the fourth hole was started in January 1991 from 9,653 metres (31,670 ft) of depth of third hole. The drilling of the fourth hole was stopped in April 1992 at 11,882 metres (38,983 ft) of depth. Drilling of the fifth hole started in April 1994 from 8,278 metres (27,159 ft) of depth of the third hole. Drilling was stopped in August 1994 at 8,578 metres (28,143 ft) of depth due to lack of funds and the well itself was mothballed.

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 12,289 metres (40,318 ft) long Al Shaheen Oil Well in Qatar.

The Soviets’ superdeep borehole isn’t alone. During the Cold War, there was a race by the superpowers to drill as deep as possible into the Earth’s crust – and even to reach the mantle of the planet itself. 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.

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 12,289 metres (40,318 ft) and a horizontal reach of 10,902 metres (35,768 ft). In terms of depth below the surface, the Kola Superdeep Borehole SG-3 retains the world record at 12,262 metres (40,230 ft) and is still the deepest artificial point on Earth.

Image Credit: Engineerine

Sources:

https://en.m.wikipedia.org/wiki/Kola_Superdeep_Borehole

https://www.bbc.com/future/