West Siberian petroleum basin

Beneath lie remnants of the Siberian traps, thought to be responsible for the Great Dying 250 million years ago.

Lower-Middle Jurassic discoveries were made in the Tyumen Formation in the 1970s, within the Krasnolenin Arch, including the Tallinn Field in 1976.

On the south, the folded Caledonian structures of the Central Kazakhstan and Altay-Sayan regions dip northward beneath the basin’s sedimentary cover.

[4] The basin is a relatively undeformed Mesozoic sag that overlies the Hercynian accreted terrane and the Early Triassic rift system.

The basement is composed of foldbelts that were deformed in Late Carboniferous–Permian time during collision of the Siberian and Kazakhstan continents with the Russian craton.

Highly organic-rich siliceous shales of the Bazhenov Formation were deposited during this time in anoxic conditions on the sea bottom.

The thick continental Aptian– Cenomanian Pokur Formation above the Neocomian sequence contains giant gas reserves in the northern part of the basin.

Volumes of discovered hydrocarbons in these systems are 144 billion barrels of oil and more than 1,300 trillion cubic feet of gas.

The largest known oil reserves are in the Bazhenov-Neocomian Total Petroleum System that includes Upper Jurassic and younger rocks of the central and southern parts of the basin.

The major part of hydrocarbon reserves is dry gas in the upper Aptian–Cenomanian sandstones (Pokur Formation and equivalents).

Source rocks for the dry gas in the Pokur Formation that constitutes more than 80 percent of the hydrocarbon reserves are unknown.

The onshore and offshore parts of the total petroleum system were assessed as separate units because of different exploration maturity and different infrastructure requirements.