The Deepest Hole in the World

      The deepest hole in the world is on the Kola peninsula of Russia near the Norwegian border. This hole is being drilled for scientific study purposes and is currently over 12,200 meters deep.
This discovery has an impact on geophysical sciences and there is a potential economic impact. This water is very highly mineralized, and is a primary concentrating agent for most ore deposits. The technology for mining at these depths is not yet available. In order to get their single drill hole down as far as they did, the Soviets had to resort to experimental methods. Their chief innovation was that, instead of turning the drill bit by rotating the stem, in the Kola well the bit alone was turned by the flow of drilling mud.

I got this information at http://www.universetoday.com/81980/deepest-hole-in-the-world/