Kola Superdeep Borehole
result of a scientific drilling project of the Soviet Union on the Kola Peninsula / From Wikipedia, the free encyclopedia
The Kola Superdeep Borehole (Russian: Кольская сверхглубокая скважина, Kolskaya sverkhglubokaya skvazhina) was a very deep hole dug on the Kola Peninsula in Russia during 1970-1992 and closed by 2008. It was dug in order to learn more about the inside of the Earth. Digging started on May 24, 1970. The work continued until 1992,[1] or 1994.[2] The borehole was kept open until 2005.[3] SG-3, the deepest part of the hole, reached 12,261 meters or 7.6 miles below the surface in 1989. That is the deepest hole ever made and is still the deepest man-made point on Earth.[2]
For a long time, SG-3 was also the longest hole by distance from its opening. In 2008, the Al Shaheen BD-04A oil well in Qatar reached +27 meters or 89 feet farther[4][5] and, in 2011, the Odoptu OP-11 oil well off Sakhalin got +83 m or 272 ft farther.[6]