The authors discuss the focal problem of regional geology: determination of the area of Kungurian deposits occurrence in North Caspian waters; namely, in the North Caspian fold and thrust zone. The Lower Permian salt-bearing Kungurian deposits play a role of regional impermeable bed for oil and gas accumulations. Absence of evaporite sequence considerably raises geological risks of hydrocarbon accumulation integrity and, thus reduces the likelihood of oil and gas field detection. 2D seismic data made the basis for the studies since there are almost no drilling data for Palaeozoic deposits in this zone. It is found that a rather thick (up to 1.5 km) evaporite sequence is present in the northern part of the North Caspian fold and thrust zone. The presented seismic and stratigraphy sections show that thickness of Kungurian deposits reduces to hundreds of metres, and then the deposits incrop below the surface of pre-Jurassic unconformity. The most ambiguous area is the Kurmangazy uplift, where single seismic survey lines demonstrate bodies morphologically associated with salt pillows. However, the presence of (thin) salt-bearing Kungurian deposits persistent over the area remains a matter of debate. The revealed patterns of the Kungurian sequence occurrence allowed concluding that northern and southern areas of the North Caspian fold and thrust zone have the lowest geological risks in terms of impermeable bed presence and integrity of hydrocarbon accumulations in Palaeozoic deposits.

Irina V. Kunitsyna
Head Specialist
RN-Exploration,
8, Mozhayskiy val street, Moscow, 121151, Russia
e-mail: ivkunitsina@rn-exp.rosneft.ru
ORCID ID: 0000-0002-7520-8303
Scopus ID: 57219708498

Aleksey V. Derduga
Candidate of Geological and Mineralogical Sciences,
Chief Project Geologist
RN-Exploration,
8, Mozhayskiy val street, Moscow, 121151, Russia
e-mail: aderduga@yandex.ru
Scopus ID: 24480804200

Vladimir E. Verzhbitskiy
Candidate of Geological and Mineralogical Sciences,
Head of Administration,
Department of Geological Exploration
Rosneft Oil Company,
31A, Dubininskaya street, Moscow, 115054, Russia
e-mail: v_verzhbitskiy@rosneft.ru
Scopus ID: 11139971900

Nikolai A. Malyshev
Doctor of Geological and Mineralogical Sciences,
Deputy Director,
Department of Geological Exploration
Rosneft Oil Company,
31A, Dubininskaya street, Moscow, 115054, Russia
e-mail: n_malyshev@rosneft.ru
Scopus ID: 24450420600

Natalya Vasileva
Senior Geophysicist
RN-Exploration,
8, Mozhayskiy val street, Moscow, 121151, Russia
e-mail: navasileva@rn-exp.rosneft.ru

Elena A. Khairullina
Deputy Director,
Department of Geological Exploration
Rosneft Oil Company,
31A, Dubininskaya street, Moscow, 115054, Russia
e-mail: EAKhairullina@rosneft.ru

1. Neftgazinform. Available at: https://oilgasinform.ru/science/fields/ (accessed 27.12.2021).

2. Kunitsyna I.V., Derduga A.V., Nikishin A.M., Korotkova M.A. Tectonic framework and history of Palaeozoic series evolution in Northern Caspian. Geologiya nefti i gaza. 2020;(3):11–18. DOI: 10.31087/0016-7894-2020-3-11-18. In Russ.

3. Abilkhasimov Kh.B. Osobennosti formirovaniya prirodnykh rezervuarov paleozoiskikh otlozhenii Prikaspiiskoi vpadiny i otsenka perspektiv ikh neftegazonosnosti [Features of natural reservoirs formation in Palaeozoic deposits of Caspian Depression, and assessment of their petroleum potential]. Moscow: Izdatel’skii dom Akademii Estestvoznaniya; 2016. 244 p. In Russ.

4. Glumov I.F., Malovitskii Ya.P., Novikov A.A., Senin B.V. Regional’naya geologiya i neftegazonosnost’ Kaspiiskogo morya [Regional geology and oil and gas potential of the Caspian Sea]. Moscow: Nedra-Biznestsentr; 2004. 342 p. In Russ.

5. Volozh Yu.A., Parasyna V.S. Astrakhanskii karbonatnyi massiv. Stroenie i neftegazonosnost’ [Astrakhan carbonate massif. Structure and petroleum potential]. Moscow: Nauchnyi mir; 2008. 222 p. In Russ.

6. Pronin A.P., Shestoperova L.V. Lower Permian deposits of the North Caspian uplift (North part of water area of the Caspian sea, Kazakhstan). Nedra Povolzh’ya i Prikaspiya. 2020;(101):37–47. DOI:10.24411/1997-8316-2020-11013. In Russ.

7. Pronin A.P., Shestoperova L.V. Lithological and stratigraphic characteristics of the рre-jurassic deposits of the North Caspian uplift. Nedra Povolzh’ya i Prikaspiya. 2019;(99):35–47. DOI: 10.24411/1997-8316-2019-19902. In Russ.

8. Bloki Kazakhstanskoi chasti Kaspiiskogo shel’fa. Perspektivy neftegazonosnosti [Blocks of the Kazakhstan part of Caspian Shelf. Petroleum potential]. Almaty; 2003. 119 p. In Russ.

9. Voronin N.I., Mitalev I.A., Makarova A.M., Prosyankin D.N. Fillipovskie otlozheniya — novyi perspektivnyi gorizont na yugo-zapade Prikaspiiskoi vpadiny [Filippovsky deposits: new promising horizon in south-west of Caspian Depression]. Geologiya nefti i gaza; 1991;(5): 4–5. In Russ.

10. Goryunov E.Yu., Ignatov P.A., Klement’eva D.N., Seravina T.V. Formation conditions of salt-dome structures in the Northern edged zone of Caspian area. Geologiya nefti i gaza; 2010;(2):29–35. In Russ.

11. Kunitsyna I.V., Derduga A.V., Al’mendinger O.A., Malyshev N.A., Khairullina E.A., Verzhbitskii V.E., Mityukov A.V. Regional geological model as a basis for substantiation of new directions of hydrocarbon prospecting in well-studied shelf regions (on the example of the North Caspian). Neftyanoe khozyaistvo. 2021;(9):23–27. DOI: 10.24887/0028-2448-2021-9-23-27. In Russ.