Models of Hydrocarbon-Bearing Sequences of West Siberia
MKRTOHYAN, O. M., G. N. GOGONENKOV, and N. E. PAVLOV, Central Geophysical Expedition, Moscow, U.S.S.R.
The West Siberian province located within a young plate (platform) is one of the largest in the world in size, reserves, number of unique fields, and hydrocarbon production. The southern, central, and western areas of the province are dominantly oil-bearing, the northern portion gas-bearing. All commercial reserves are within the Devonian-Cenomanian stratigraphic interval. Small accumulations in fractured-vuggy Devonian-Carboniferous rocks are located in the zone of unconformity between this sequence and the Jurassic. The potential of the pre-plate middle Paleozoic, platform upper Paleozoic, and Triassic sequences recognized by seismic data in the northern, deepest, part of the plate is not known yet.
Most hydrocarbon pools are located in the Jurassic-Cretaceous hydrocarbon-bearing sequences (HBS) within the plate cover. Structural-depositional oil accumulations with very changeable flow rates, a large stratigraphic-depositional accumulation in high permeability basal (quartz) reservoirs, and an oil-condensate and a multiple-pool structural gas field are discovered in the Middle Jurassic composed of potential continental coal-bearing and marine deposits.
The Callovian-Kimmeridgian (Vasugan) HBS where numerous medium and high-production fields were discovered in traps of various type and which is dominantly composed of shallow-water marine terrigenous deposits is located mainly in the southeastern, central, and partly western (near Urals) areas.
The Volgian-Neocomian sequence is characterized by the formation of a very large starved basin, a unique layer of high-bitumen Bazhenov shale, a large progradational sequence, and a polycyclic Neocomian shelf sequence containing giant hydrocarbon fields.
The Barremian-Berrisian progradational sequence represented by a series of clinoforms and extending over 1600 km is characterized by cross-bedding, semi-regional, low-quality reservoirs with oil (low-production) and oil-condensate fields.
The Neocomian shelf HBS comprising regional high-permeability reservoirs has the greatest oil reserves most of which are contained in the large unique fields in the Middle Ob region.
The Aptian-Albian-Cenomanian coal-bearing continental and coastal deposits of the northern area are associated with the dominant gas-bearing area including unique fields that account for more than 75% of the total gas reserves of the province.
In most HBS, there is still a prospect of discovering new hydrocarbon pools including pools in more complex traps.
AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)