--> Abstract: Relationship between Source Rocks and Distribution of Oil and Gas Fields in West Siberia, by N. N. Nemchenko and A. Rovenskaya; #90987 (1993).

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NEMCHENKO, NILOLAY N., State Commission of Mineral Reserves, Moscow, Russian Federation; and ALLA ROVENSKAYA, Institute of Geology and Exploration of Combustible Fuels, Moscow, Russian Federation

ABSTRACT: Relationship between Source Rocks and Distribution of Oil and Gas Fields in West Siberia

In the West Siberia there are 396 HC fields. The total number of pools is 1512, of which 1053, 107 and 352 pools contain oil, oil-gas and gas-condensate, respectively. The pools are found at depths from 600 to 5000 m in the temperature interval from 15 to 150 degrees C. They associate with continental and marine rocks. Zonation of the pool distribution is in aperfect accordance with the oil and gas source rock distribution. There are 6 source rock units, each being simultaneously a HC producing unit (Lower Jurassic, Vasiugan, Bazhenov, Achimov, Neocomian and Aptian-Albian-Cenomanian). The phase state of HC systems is essentially controlled by their generation conditions. Predominance of sapropelic OM has provided for formation of oil pools in the Sredne-Ob OGA, Krasnoleninsk and Salym OGR. Predominance of humic OM known to promote the generation of gas and gas-condensate in the north of West Siberia. The formation of the major zone of prevailingly gas accumulation in the north of West Siberia associates with the evolution of the coal-bearing seguence. The association of gas accumulations with coal-bearing deposits, the compositional features of the natural gases practically devoid of heavy HC, the similarity of absolute values of carbon isotopic characteristics measured for the methane from gas pools and marshes, and the scale of generation of gases and balance of their distribution, are all in favor of the conclusion that the OM of low stages of catagenesis (its coalified remains are present all over the Cenomanian rock seguence) was the principal source of gas for t e Cenomanian pools, during their formation. The Upper Jurassic Bazhenov Unit is an excellent source rock. This Unit has proved to be a prolific shale recovery. More than 300 wells have been drilled to date in the area, covering approximately 5800 sq km. About 10% of potential petroleum reserves of Mezozoic sedimentary cover are concentrated in Bazhenov petroleum-bearing complex. The Bazhenov formation is composed of calcerous, organic-rich mudstone and siliceous shalelithofacies. The main feature of this complex is the relation of the pools to a unique type of reservoir Bazhenov of clay- silica- lime composition with a high content of organic matter. The oil pools are related to a zones with high temperature "hot spot" (Salym oil field the major discovery).

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.