What’s The Deepest Borehole To Have Ever Been Drilled?

by | Jan 7, 2021

During the Cold War, things across the world got more than a little bit, well, weird on several occasions. From face mask disguises to threats to detonate nuclear warheads on the moon, there was a very real risk of events boiling over into a full-scale global, nuclear war – which is ironic, really, when you consider the fact it’s called the Cold War.

One of the weirdest events, however, was the construction of the Kola Superdeep Borehole in Russia, in 1979. Never heard of it? Well, we’re not surprised. That’s why the team here at Borehole Solutions, who offer a range of geotechnical services, both in the UK and internationally, wanted to explore the story of the deepest artificial borehole ever drilled…


The Beginnings

The Kola Peninsula sits on the north-western outreaches of modern-day Russia, near to the Norwegian border. The Soviet Union first began drilling boreholes there in May, 1970, using the now archaic Uralmash-4E drilling set-up. Their reason? Well, officially it was for scientific research (just as the US’ equivalent project was for scientific research) but really it was a show of might.

The height of the cold war saw the USA and the Soviet Union pitting themselves against one another in increasing shows of social, political, economic, technological and military peacocking. The most famous example of this is the ‘Space Race’ but if extended to so many other areas, as well. Put it this way, if there was something to be the biggest or best at, you can guarantee the two nations were trying their hardest to secure that title.

The deepest borehole wasn’t actually drilled until almost two decade later, however, in 1989. This borehole was named SG-3 (catchy, we know) and it’s fair to say that this borehole gave the premise of the ‘journey to the centre of the earth’ a fair crack of the whip…


How Deep Did It Go?

In terms of true vertical depth, SG-3 came in at a staggering 7.619 miles. That’s over 12.2 Km in metric measurements, but whether you measure in old or new money, that’s a heck of a long way down. They didn’t want to stop there either! Not content with simply holding the record, the Soviets were intent on drilling even deeper. Unexpected changes in density and temperature, however, made this unfeasible.

Present-Day Borehole Drilling Services

That original borehole has now been welded shut (though you can still find it, if you’re curious) and the project was shut down in the ‘90s, coinciding with the Soviet Union’s dissolution. Today, there are numerous deep borehole projects, the most exciting of which perhaps being a project to drill through the earth’s crustand into the mantle.

The crust is the outermost part of our planet and acts exactly like its name – a crust. Beneath is the mantle, which comprises around 85% of the earth’s overall volume. No drilling project has ever managed to reach the mantle, but this looks set to change this decade. The Japanese drilling vessel Chikyū is part of the Integrated Ocean Drilling Program (IODP). Its ultimate plans are to drill beneath the earth’s crust, at one of its thinnest points, in what would be a momentous occasion for the geotechnical community.


Facts About The Kola Superdeep Borehole

  • It had its own commemorative run of stamps produced after its construction!
  • Although its record in terms of measured depthhas now been surpassed, SG-3 still retains the world record for deepest ever borehole, in terms of true vertical depth.
  • To drill as deep as they did, the Soviets had to design an entirely new drill because their previous technology wasn’t capable of reaching those new depths!


Contact Borehole Solutions 

It’s fair to say that our borehole services are a bit more conventionalthan the drilling carried out in the wilds of Russia. We offer a huge range of drilling services, including sonic,rotary, cable percussive,restricted access, remediationand more! If you’d like to find out more, then get in touch! Contact Borehole Solutions today or head over to our Instagram to take a look at some of our previous work.