Misplaced Pages

#342657

34-830: 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. Gas was discovered in 1953 in Upper Jurassic sandstones and limestones , within the Berezov Field. Then in 1960, oil

68-668: A distance of 3,530 km (2,193 mi) to the Arctic Ocean, where it discharges more than 20 million litres (5 million gallons) of water per second at its mouth. Together with its tributary Angara, the two rivers flow 5,530 km (3,436 mi). The valley formed by the Yenisei acts as a rough dividing line between the West Siberian Plain and the Central Siberian Plateau . The Siberian Uvaly

102-612: Is a large plain that occupies the western portion of Siberia , between the Ural Mountains in the west and the Yenisei River in the east, and the Altai Mountains on the southeast. Much of the plain is poorly drained and consists of some of the world's largest swamps and floodplains. Important cities include Chelyabinsk , Novosibirsk , Omsk , and Tomsk , as well as Surgut and Nizhnevartovsk . Winters on

136-702: Is a low hilly region stretching from east to west across the plain. Glacial deposits extend as far south as the Ob-Irtysh confluence, forming occasional low hills and ridges, including the Ob Plateau in the south, but otherwise the plain is exceedingly flat and featureless. The Ishim Plain and the Baraba Lowland in the south are important agricultural areas. There are salt lakes in the Kulunda Plain , which extends southwards into Kazakhstan and

170-681: Is a region of the Earth's crust that has undergone prolonged subsidence and is composed of horizontal deposits from as much as 65 million years ago. Many of the deposits on this plain result from ice dams that reversed the flow of the Ob and Yenisei rivers, redirecting them into the Caspian Sea , and perhaps the Aral Sea as well. Berriasian In the geological timescale , the Berriasian

204-645: Is an age / stage of the Early/Lower Cretaceous . It is the oldest subdivision in the entire Cretaceous . It has been taken to span the time between 145.0 ± 4.0 Ma and 139.8 ± 3.0 Ma (million years ago). The Berriasian succeeds the Tithonian (part of the Jurassic ) and precedes the Valanginian . The Berriasian Stage was introduced in scientific literature by Henri Coquand in 1869. It

238-577: Is defined by the base of the Valanginian, which is fixed at the first appearance of calpionellid species Calpionellites darderi . This is just a little below the first appearance of the ammonite species Thurmanniceras pertransiens . Regional terms used in Russia include "Volgian"(which spans perhaps the latest Kimmeridgian, all the Tithonian and an uncertain amount of the lower Berriasian) and

272-621: Is largely absent, rich grasslands that are an extension of the Kazakh Steppe formed the original vegetation, which had almost all been cleared by the early 21st century. The West Siberian Plain consists mostly of Cenozoic alluvial deposits and is extraordinarily flat. A rise of fifty metres in sea level would cause all land between the Arctic Ocean and the Ob - Irtysh confluence near Khanty-Mansiysk to be inundated (see also Turgai Straits , West Siberian Glacial Lake ). It

306-502: Is limited to the south by the Kokshetau Hills . The West Siberian Plain is very swampy and soils are mostly peaty Histosols and, in the treeless northern part, Histels . is one of the world's largest areas of peatlands, which are characterized by raised bogs . Vasyugan Swamp , one of the world's largest single raised bogs, covers approximately 51,600 square kilometres (19,900 sq mi). There are numerous lakes in

340-630: Is named after the village of Berrias in the Ardèche department of France . The largely non-marine English Purbeck Formation is in part of Berriasian age. The first rocks to be described of this age were the beds of the English Purbeck Formation, named as the Purbeckian by Alexandre Brongniart in 1829 following description by Henry De la Beche , William Buckland , Thomas Webster and William Henry Fitton . The base of

374-501: The Arctic Ocean to the foothills of the Altai Mountains , and from east to west for 1,900 km (1,181 mi) from the Yenisei River to the Ural Mountains . Besides the Yenisei, other main rivers in the West Siberian Plain are from west to east the Irtysh , Ob , Nadym , Pur and Taz . There are many lakes and swamps and large regions of the plains are flooded in the spring. The long Yenisei River flows broadly south to north,

SECTION 10

#1732764881343

408-726: 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 Tallinn 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

442-636: 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

476-532: 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. The basin occupies a swampy plain between

510-675: The Bazhenov-Neocomian Total Petroleum System that includes Upper Jurassic and younger rocks of the central and southern parts of the basin. Oil reservoirs are mainly in Neocomian and Upper Jurassic clastic strata. Source rocks are organic-rich siliceous shales of the Bazhenov Formation. Most discovered reserves are in structural traps, but stratigraphic traps in the Neocomian clinoform sequence are productive and are expected to contain much of

544-715: The Berriasian, which is also the base of the Cretaceous System , has traditionally been placed at the first appearance of fossils of the ammonite species Berriasella jacobi . But this is a species that has a stratigraphically problematic and geographically limited distribution. A global reference profile (a GSSP ) for the Berriasian has been under active consideration by the Berriasian Working Group (ISCS) of IUGS since 2010. A range of contender GSSP localities has been studied in detail by

578-726: The Neocomian sequence contains giant gas reserves in the northern part of the basin. 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. Three total petroleum systems are identified in the West Siberian 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 assessed mean undiscovered resources are 55.2 billion barrels of oil, 642.9 trillion cubic feet of gas, and 20.5 billion barrels of natural gas liquids . The largest known oil reserves are in

612-537: 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

646-516: The West Siberian Plain are harsh and long. The climate of most of the plain areas is either subarctic or continental. The plain had large petroleum and natural gas reserves. Most of Russia's oil and gas production was extracted from this area during the 1970s and 80s. The West Siberian Plain is located east of the Ural Mountains mostly in the territory of Russia . It is one of the Great Russian Regions and has been described as

680-808: The Working Group including localities as far apart as Mexico, Ukraine, Tunisia, Iraq and the Russian Far East. Several markers have been employed to refine correlations and to work towards defining a base for the Berriasian Stage. These include calcareous microfossils , such as Nannoconus , calpionellids , ammonites , palynological data and magnetostratigraphy , notably magnetozone M19n. The calibration of these markers, especially Nannoconus steinmannii minor , N. kamptneri minor , and Calpionella alpina , within precisely fixed magnetozones give greater precision in trying to identify

714-531: The base of the Alpina Subzone in the middle of magnetozone M19n.2n. This site proposal, of Tré Maroua, was subsequently unsuccessful in a vote of the ISCS (8 votes for and 8 against: 4 not voting); a new working group was formed in 2021. In the western part of the ocean of Tethys , the Berriasian consists of four ammonite biozones , from top to bottom (latest to earliest): The top of the Berriasian stage

SECTION 20

#1732764881343

748-556: 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

782-658: The basin are included in the Northern West Siberian Mesozoic Composite Total Petroleum System that encompasses the entire sedimentary cover. The system is strongly gas-prone; it contains giant gas reserves and comparatively small oil reserves. The major part of hydrocarbon reserves is dry gas in the upper Aptian–Cenomanian sandstones (Pokur Formation and equivalents). Smaller reserves of wet gas and some oil are in Jurassic and Neocomian sandstones. Source rocks for

816-546: The best position for a boundary. In 2016, the Berriasian Working Group voted to adopt Calpionella alpina as the primary marker for the base of the Berriasian Stage. In 2019, a GSSP for the Berriasian was nominated by a vote of the Berriasian Working Group of the Cretaceous Subcommission (ISCS): it is the profile of Tré Maroua in the Vocontian Basin (Hautes Alpes, France). The GSSP was defined at

850-479: The dry gas in the Pokur Formation that constitutes more than 80 percent of the hydrocarbon reserves are unknown. Wet Neocomian gas and oil were generated from Jurassic source rocks, including the Bazhenov Formation. Almost all discovered reserves are in structural traps; however, stratigraphic traps in the Neocomian interval probably contain large undiscovered gas resources. The onshore and offshore parts of

884-527: The same geographic area as the Bazhenov-Neocomian system, but it includes older, Lower–Middle Jurassic strata and weathered rocks at the top of the pre-Jurassic sequence. A Callovian regional shale seal of the Abalak and lower Vasyugan Formations separates the two systems. The Togur-Tyumen system is oil-prone; gas reserves are insignificant. The principal oil reserves are in sandstone reservoirs at

918-495: 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

952-665: The south, the folded Caledonian structures of the Central Kazakhstan and Altay - Sayan regions dip northward beneath the basin’s sedimentary cover. 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

986-647: The top and bottom of the Lower–Middle Jurassic Tyumen Formation; comparatively small reserves are in pre-Jurassic carbonate and clastic rocks. The principal source rocks are lacustrine to marine shales of the Toarcian Togur Bed. Traps are structural, stratigraphic, or a combination of the two. The total petroleum system was assessed as a single assessment unit. Most of the undiscovered resources are expected in stratigraphic and combination traps. The northern onshore and offshore parts of

1020-603: The total petroleum system were assessed as separate units because of different exploration maturity and different infrastructure requirements. The onshore area is substantially explored, especially in the shallow Aptian–Cenomanian sequence, whereas only three exploratory wells have been drilled offshore. Undiscovered gas potential of both assessment units is very high. West Siberian plain The West Siberian Plain ( Russian : Западно-Сибирская равнина , romanized :  Zapadno-Sibirskaya ravnina )

1054-569: The undiscovered resources. Two assessment units are identified in this total petroleum system. The first assessment unit includes all conventional reservoirs in the stratigraphic interval from the Upper Jurassic to the Cenomanian. The second unit includes unconventional (or continuous), self-sourced, fractured reservoirs in the Bazhenov Formation. This unit was not assessed quantitatively. The Togur - Tyumen Total Petroleum System covers

West Siberian petroleum basin - Misplaced Pages Continue

1088-463: The vast interfluve swamps of the Ob-Taz floodplain . The plain has eight distinct vegetation regions: tundra , forest-tundra, northern taiga , middle taiga, southern taiga, sub-taiga forest, forest-steppe, and steppe . The number of animal species in the West Siberian Plain ranges from at least 107 in the tundra to 278 or more in the forest-steppe region. In the south of the plain, where permafrost

1122-413: The world's largest unbroken lowland – more than 50 percent is less than 100 m (328 ft) above sea level —and covers an area of about 2.6–2.7 million square kilometres (1.0 million square miles) which is about one third of Siberia. It extends from north to south for 2,500 kilometres (1,600 miles), reaching its maximum width of 1,500 kilometres (930 miles) in its southern part. from

1156-784: 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

#342657