It sinks more than 12 kilometers below the surface of the earth. SG-3, the “Super Deep Kola Experimental Reference Well” in Russia, is the deepest hole ever dug by man. But the opening was finally sealed in 2005 without ever achieving the goal set by the researchers: to dig up to 15 km deep.
12,262 meters. Here is the depth of the “Kola experimental super deep reference well” named SG-3 in Murmansk region, Russia. For comparison: That corresponds to almost 38 Eiffel Towers, 132 Statues of Liberty, 122 soccer fields, 3 million table tennis balls or even 1.3 Mount Everest. In short, it’s deep.
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Battle for space, battle for depth
And the depth of this hole, which stopped drilling in 1995, has never been reached since. But back to the origin of the project. 1970. The Soviet Union has just lost the battle for space since American Neil Armstrong stepped on the moon on July 21, 1969. A pity! The Soviets will win another battle: that of the deepest hole ever dug.
The Americans, too, had attempted to drill a hole near the island of Guadalupe (Mexico) with the Mohole project (1961-1966), reaching a depth of 3,653 meters.
Kola’s SG-3 well in 1974. (Photo: Yuri Yakovlev Archive / Wikimedia Commons / CC.BY.SA.4.0)
The entrance to the Kola Experimental Super Deep Reference Well or SG-3. (Photo: Alexander Novikov/Wikimedia Commons)
Target: 15 km deep
But the Soviets are more ambitious. They have set themselves the goal of reaching a depth of 15 km. For 23 cm diameter. On May 24, 1970, they began drilling. Scientists have dug tirelessly for 22 years since the project began. The then world depth record was broken on June 6, 1979 by Bertha Rogers’ 9,583 meter deep hole dug in Washita County, Oklahoma (USA) to search for oil.
Scientists are looking. According to Pet’r Skufin, a scientist at the Geological Institute of the Kola Science Center and the author of the article “Anniversary of the start of drilling work on the deep well SG-3 Kola”, they want to study the structure and composition of the soils and improve ultra-deep drilling techniques and technologies. And they make several discoveries.
First, microscopic fossils of 24 species of long-dead unicellular plankton were found along the entire borehole to a depth of 6.7 kilometers. You will also find water that comes from the minerals of the earth’s deep crust and has never been able to reach the surface due to an impermeable layer of rock.
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The Kola Superdeep well (SG-3). The vertical tower and drilling machine, the Uramash 15,000. (Photo: Gate Research / CC BY-NC-ND 4.0)
The problems
In 1983 the well exceeded the 12,000 meter mark. But the problems are piling up. On September 27, 1984, after sinking to 40,000 feet (12,066 m), a 2,000-millimeter (5,000-millimeter) section of drill string twisted and lodged in the hole. “Assembled from special, heavy-duty aluminum alloy drill rods and placed in weighted drilling mud, the drill string could not withstand the enormous loads and began to stretch like stone. Rubber”, sums up Pet’r Skufin. This problem repeats itself several times and slows down the drilling process.
Worse, scientists face a major problem: heat. While they thought the temperature of the rocks at 12 km depth would be around 100 °C, it actually rises to 180 °C. This implies “Repeated accidents, breakages and loss of drill rigs”, emphasizes the researcher.
The center of the experimental superdeep reference well Kola (SG-3), September 24, 2020. (Photo: Shelkovnikov Evgeny / Wikimedia Commons / CC.BY.SA.4.0)
In 1991 the project received the final blow. The USSR collapses and the research center begins to decay. The then 12,262 meter deep well was officially stopped in 1992.
Since then, work has never resumed and the center has fallen into disrepair. However, Kola’s drilling depth record remains unsurpassed and is in the Guinness Book of Records. At 10,994 meters, it even surpasses the deepest point in the ocean, the Mariana Trench.