The 50th Anniversary of the Start of Drilling the Kola Superdeep Well

The Kola Superdeep Well (SG-3) is an outstanding achievement of Soviet science and technology, drilled in Precambrian crystalline rocks and reached a depth of 12262 m. It was one of a series of super deep wells planned within the framework of the program “Earth's Interior Exploration and Superdeep Drilling”. In order to achieve record depths, unique domestic drilling equipment and materials capable of working at high temperatures and pressures were created. A fundamentally new technology for drilling wells using hydraulic downhole motors was developed. Despite difficult drilling conditions and repeated accidents, SG-3 has fulfilled almost all the tasks assigned to it. The well was penetrated with full core sampling, which was subjected to comprehensive study. This made it possible to study the deep structure of the Earth's crust and to revise the interpretation of depth seismic data. It was found that changes in the physical properties of rocks at great depths had been erroneously interpreted as a change in their composition. It made it possible to assess the prospects of deep horizons of the Pechenga structure for copper-nickel mineralisation by uncovering a previously unknown body of ore-bearing hyperbasites. New information was obtained on the temperature gradient, which turned out to be significantly higher than expected, as well as on the vertical metamorphic zoning along the borehole section. The composition and physical properties of rocks in deep horizons were investigated. Tectonic fault zones and six types of ore mineralisation were identified in the borehole section. New data on ore formation processes at great depths have been obtained, which is an important contribution to the theory of mineral deposit formation.