The West Siberian petroleum basin (also known as the West Siberian hydrocarbon province or Western Siberian oil basin) is the largest hydrocarbon (petroleum and natural gas) basin in the world covering an area of about 2.2 million km², and is also the largest oil and gas producing region in Russia.
Geographically it corresponds to the West Siberian plain. From continental West Siberia, it extends into the Kara Sea as the East-Prinovozemelsky field.
Beneath lie remnants of the Siberian traps, thought to be responsible for the Great Dying 250 million years ago.
History
Gas was discovered in 1953 in Upper Jurassic sandstones and limestones, within the Berezov Field. Then in 1960, oil was discovered in the Upper Jurassic 400 km south, in the Trekhozer Field. A Neocomian oil discovery followed in 1961, in the Middle Ob Region, followed by several giant and large fields, including the Samotlor Field. Gas was discovered in Cenomanian sandstones in 1962 within the Taz Field. This was followed by several giant and large dry gas fields in the Aptian-Cenomanian Pokur Formation, including the Medvezhye Field and Urengoy Field, which commenced production in 1972 and 1978 respectively. Lower-Middle Jurassic discoveries were made in the Tyumen Formation in the 1970s, within the Krasnolenin Arch, including the Talin Field in 1976. The giant Rusanovskoye Field and Leningrad Field were discovered in the south Kara Sea in 1989-90.
Since the early 2010s Russia's state-owned energy company Gazprom has been developing Yamal project in the Yamal Peninsula area. As of 2020, Yamal produces over 20% of Russia's gas, which is expected to increase to 40% by 2030. The shortest pipeline routes from Yamal to the northern EU countries are the Yamal–Europe pipeline through Poland and Nord Stream 1 to Germany. The proposed gas route from Western Siberia to China is known as Power of Siberia 2 pipeline.
Description
Geography
The basin occupies a swampy plain between the Ural Mountains
and the Yenisey River. On the north, the basin extends offshore
into the southern Kara Sea. On the west, north, and east, the
basin is surrounded by the Ural, Yenisey Ridge, and Turukhan-
Igarka foldbelts that experienced major deformations during the
Hercynian tectonic event and the Novaya Zemlya foldbelt that
was deformed in early Cimmerian (Triassic) time. On the south, the folded Caledonian structures of the Central Kazakhstan and Altay-Sayan regions dip northward beneath the basin’s sedimentary cover.
Geology
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. The basement also includes several microcontinental blocks with a relatively undeformed Paleozoic sedimentary sequence.
The sedimentary succession of the basin is composed of
Middle Triassic through Tertiary clastic rocks. The lower part of
this succession is present only in the northern part of the basin; southward, progressively younger strata onlap the basement, so that in the southern areas the basement is overlain by Toarcian and younger rocks. The important stage in tectono-stratigraphic development of the basin was formation of a deep-water sea in Volgian–early Berriasian time. The sea covered more than one million km 2 in the central basin area. Highly organic-rich siliceous shales of the Bazhenov Formation were deposited during this time in anoxic conditions on the sea bottom. Rocks of this formation have generated more than 80 percent of West Siberian oil reserves and probably a substantial part of its gas reserves. The deep-water basin was filled by prograding clastic clinoforms during Neocomian time. The clastic material was transported by a system of rivers dominantly from the eastern provenance. Sandstones within the Neocomian clinoforms contain the principal oil reservoirs. The thick continental Aptian– Cenomanian Pokur Formation above the Neocomian sequence contains giant gas reserves in the northern part of the basin.
Oil and gas reserves
The Western Siberian oil basin is the largest oil and gas producing region in Russia. The oil extracted in this territory accounts 70% of the oil produced in the country.