West siberia basin

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Location of West Siberian Basin[1]
North and Central Part of West Siberian Basin
West Siberian Structural Map [2]

Introduction

The West Siberian Basin is located on continental West Siberia and goes all the way to the Kara Sea. This is the worlds largest Hydrocarbon basin sitting at around 2 million km2. underneath this behemoth of a basin is believed to lie what is left of the Siberian traps which were believed to cause the Great Dying 250 mil years ago. [3]

History

Throughout the different areas of the West Siberian Basin, gas and many other elements were discovered at different times. In 1953, gas was discovered in the Upper Jurrasic Sandstones and Limestone of the berezov field.Seven years later in 1960, more gas was found about 400km south of the original location in Upper Jurassic. This area was known as Trekhozer field. The following year a new oil discovery was found, it was Neocomian oil. The location of this discovery was in the Middle Ob Region. Following that discovery there , gas was discovered in the year 1962 in the Cenomanian Sandstones which are located around the Taz Field. In the Aptian-Cenomanian Pokur Formations there was multiple Dry gas fields that were discovered including the Medvezhye and Urengoy Fields. These fields started production around the years 1972 and 1978. The latest things that were apart of the history of this basin were made in the lower-middle Jurassic when the discoveries were made in the Tyumen Formation during the 1970's. There were two giant fields that were discovered in the South Kara Sea during the years 1989-1990. the two fields that were discovered in the Sea were Rusanovskoye Field and Leningrad Field.[4]

Primary Risk and Uncertainties

The primary risks and uncertainties that go along with this basin are not things that are of great danger to anybody but more so how will the basin be able to be produced when it comes to the possible drilling locations. The basin itself has the most potential being that there is so much land and area that is still unexplored. The main risk and uncertainty is where does one company start. there are many studies that have been done trying to read the ground underneath the basin to discover possible leads to the most rich and prospering locations that this basin has to offer.[5] There is just so much uncertainty that is associated with the basin that more research is continuing to be done daily to combat this. The technology that has been created now is allowing for researchers and scientist to understand where there is better potential but there has still been a struggle to perfect the overall results of the technology they are using. The biggest uncertainty is " gas could not be positively correlated to any of several potential petroleum source rocks". [6]

Petroleum Elements

Seal-

Four petroleum-promising megacomplexes overlain bymegaregional seals in the roof are recognized in the WestSiberian sedimentary cover: Jurassic, Neocomian, Aptian–Al-bian–Cenomanian, and Turonian–Danian. They are subdi-vided into petroleum-promising complexes by zonal and localshale members.The Jurassic megacomplex is overlain by the BazhenovoFormation and coeval strata (Upper Jurassic, Volgian); theNeocomian one, by the Koshai member of the Alym Forma-tion (Lower Cretaceous, Aptian); the Aptian–Albian–Cenoma-nian megacomplex, by the Kuznetsov Formation (UpperCretaceous, Turonian); and the Turonian–Danian megacom-plex, by the Talitsa Formation (Paleocene, Danian)

Source Rock and Migration-

Organic-rich, calcareous shales of the Bazhenov Formation are the primary source rocks of the Bazhenov-Neocomian. Within the West Siberian basin, 90 percent of the oil reserves lie within these rocks . The Bazhenov Formation is about 20-40m in depth; however locally the thickness grows to 50–60 m throughout. The area of this formation is almost one million kilometers and holds about eighteen trillion tons of organic matter.[4] Only recently, when the geologists received access to modern geochemical analytical equipment, did it become clear that most of oils of the TPS were derived from organic-rich shales of the lower Toarcian Togur Bed in the lower part of the Tyumen Formation.[4] There are many different types of source rocks that come from the basins of West Siberia and there are so many more examples that i believed to not be discovered yet.

Reservoir Rocks-

Two groups of clastic reservoir rocks are present in this Basin. The first group includes reservoir rocks (primarily in the Megion and Vartov Formations) that were deposited on shelves of clinoforms east of their basinward slopes and in the upper part of the Vartov Formation that overlie the clinoforms. This group produces the most rich reservoirs of the West Siberian basin. The second group of Neocomian reservoir rocks includes sandstones and siltstones which are primarily located in the diachronous Achimov Formation deposited on slopes and in adjacent parts of the deep sea. Original oil production from wells in many fields was several hundred to a few thousand barrels per day[4]

Trap-

Most of the discovered oil and gas reserves of the Bazhenov-Neocomian TPS are in structural traps. These traps contain all giant oil fields of the TPS except for the Priob field, in which major reserves are in a system of stratigraphic traps. The Traps in this part of the basin are platform-type anticlinal uplifts with dips seldomly exceeding two degrees.[4]Stratigraphic and combination structural and stratigraphic traps are dominant in the Togur-Tyumen TPS. there have been many pools that have been discovered in the basal part of the Tyumen Formation, all of which have been labeled as stratigraphic traps. These pools are mainly located in low structured areas that are made of shoestring sandstone bodies that are deposited in river valleys.[4]

Petroleum Potential

The West Siberian basin is among world largest petroleum stores. The basin has been largely explored through the recent decades with thousands of kilometers of reflection profiles and about 200,000 drill holes that have yielded hundreds of oil and gas discoveries with tens of BBOE oil and about a hundred cf gas production[7]. Recently deployed 3D seismic exploration and painstaking processing of the reflection data reveal new details of the basin architecture with new implications for the tectonic history, which call for a revision of the existing models for some large oil and gas fields[7]. Four petroleum-promising megacomplexes overlain by megaregional seals in the roof are recognized in the West Siberian sedimentary cover: Jurassic, Neocomian, Aptian–Al-bian–Cenomanian, and Turonian–Danian.[8]

Facility Engineering

The most important results of the development of the structural model for the assessment of petroleum potential relate to the South-West Barents Sea and show a classical rift system with major extensional faults.The process of our investigations included several stages, from the processing of geophysical data to their qualitative and quantitative interpretation followed up by the compilation of geological-structural schemes[9]

Additional Readings

https://pubs.usgs.gov/bul/2201/G/B2201-G.pdf

https://pubs.usgs.gov/pp/1824/q/pp1824q.pdf

https://www.le.ac.uk/gl/ads/SiberianTraps/Introduction.html

References

  1. Online journal For E&P Geoscientists. (2015, November 2). Retrieved May 11, 2021, from https://www.searchanddiscovery.com/pdfz/documents/2015/10784sobornov/ndx_sobornov.pdf.html
  2. Ulmishek, G. (n.d.). USGS bulletin 2201-G: PETROLEUM geology and resources of the West SIBERIAN Basin, Russia. Retrieved May 11, 2021, from https://pubs.usgs.gov/bul/2201/G/
  3. Siberian traps - Introduction. (n.d.). Retrieved May 11, 2021, from https://www.le.ac.uk/gl/ads/SiberianTraps/Introduction.html
  4. 4.0 4.1 4.2 4.3 4.4 4.5 Ulmishek, G. F., 2003, Petroleum Geology and Resources of the West Siberian Basin, Russia. U.S. Geological Survey Bulletin 2201-G, https://pubs.usgs.gov/bul/2201/G/B2201-G.pdf
  5. Braitenberg, C., & Ebbing, J. (2009, June 03). New insights into the basement structure of the West SIBERIAN basin from forward and inverse modeling of Grace satellite gravity data. Retrieved May 11, 2021, from https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2008JB005799
  6. Schenk, C. J. (2008). Geology and Assessment of Undiscovered Oil and Gas Resources of the Northern West Siberian Mesozoic Composite Total Petroleum System of the West Siberian Basin Province, Russia, [PDF]. Reston.
  7. 7.0 7.1 Gogonenkov, G. N. (2009, January 13). Strike-slip faults in the West Siberian basin: Implications for petroleum exploration and development [PDF].
  8. Kontorovich, V. A. (2008, October 21). The Meso-Cenozoic tectonics and petroleum potential of West Siberia [PDF].
  9. Deep Structure, Tectonics and Petroleum Potential of the Western Sector of the Russian Arctic [PDF]. (2021, March 1).