Post-Cenomanian gas bearing megasequence in the north of the Western Siberia contains a number of independent gas sequences, they are: Gazsalinsky, Nizhneberezovsky, Verkhneberezonsko-Gan’kinsky, Tibeisalinsko-Lyulinvorsky, and Atlymsko-Chetvertichny. Commercial gas content where gas is difficult-to-recover is determined in Gazsalinsky and Nizhneberezovsky sequences, while in the others, only gas manifestations of varying intensity are observed. Through the lens of deep naphtidogenesis, the post-Cenomanian gas bearing megasequence is considered as a main zone of deep high-pressure steam-gas flow discharge, which determines its high gas saturation and potential in gas-bearing territories of the basin. Numerous reservoir-type seismic anomalies (flat spots) are observed in the post-Cenomanian gas bearing megasequence, they are supported by higher resistivity of reservoir rocks and gas manifestations in wells. The authors believe that high-rate emergency gas blowouts in Gubkinsky (1965) and Varyogansky (1972) fields are associated with the post-Cenomanian gas bearing megasequence. They expect numerous gas hydrate accumulations both in thermobaric zone of gas hydrate stability and beyond it – in the metastability zone, where gas hydrates slowly melt. The studies carried out allow considering the post-Cenomanian gas bearing megasequence as highly promising, with in-place gas resources of about 200 TCM of gas a considerable part of which can be found above the Cenomanian gas pools being produced.

Aleksei A. Nezhdanov  ORCiD 
Doctor of Geological and Mineralogical Sciences,
Professor
ZapSibNIIGG,
48/4a, ul. Respubliki, Tyumen,625000, Russia
e-mail: nezhdanovaa@zsniigg.ru

​Ol’ga A. Vazhenina  ORCiD 
Candidate of Geological and Mineralogical Sciences,
Head of Department
ZapSibNIIGG,
48/4a, ul. Respubliki, Tyumen, 625000, Russia
e-mail: VazheninaOA@zsniigg.ru

Evgeniya V. Trigub
Head of the laboratory
ZapSibNIIGG,
48/4a, ul. Respubliki, Tyumen, 625000, Russia
e-mail: SmirnovaEV@zsniigg.ru

​Aleksei V. Trigub 
Head of Division
ZapSibNIIGG,
48/4a, ul. Respubliki, Tyumen, 625000, Russia
e-mail: TrigubAV@zsniigg.ru

Irina V. Privalova
Head of the laboratory
ZapSibNIIGG,
48/4a, ul. Respubliki, Tyumen, 625000, Russia
e-mail: PrivalovaIV@zsniigg.ru

​

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