Salym; potential giant oil field in West Siberia; possible reservoir stimulation experiment using a nuclear explosion

A seismic event of October 4, 1979, east of the Ural Mountains was described by the U. S. Department of Energy as an underground nuclear explosion. The location of this event by the U.S. Geological Survey places it in the oil-rich Middle Ob region of West Siberia in the vicinity of the Salym oil field. The field, which was discovered in 1965, has seven oil pools, of which the main pay is the bituminous shale of the Upper Jurassic Bazhenov Formation. This formation is one of the few examples of a primary oil-bearing pelite reservoir having a high content of organic matter that was also the source of the oil. A characteristic of the Bazhenov Formation is the wide range of fracture permeability and oil flow rates. Where fracture permeability is high, wells yield more than 2,100 bbl/day. Elsewhere, wells yield less than 35 bbl/day or are dry. The seismic event of October 4, 1979, may have been an underground nuclear explosion experiment designed to stimulate production by fracturing the tight bituminous shale. Previous attempts to stimulate oil production in the U.S.S.R. by using nuclear explosions were carried out in carbonate reservoirs.