Geological structure of the wendian and the wendian-cambrian natural reservoirs of the south-eastern part of the Angaro-Lena stage oil and gas exploration results

Background. The results of a new stage of exploration for hydrocarbon raw materials at the beginning of 2023 along the southern part of the Verkhnelensk Mesocainozoic arch lifting, which is limited to Zhigalovsky and Bozhekhansky mega-anticlines in the southeastern part of the Angara-Lena stage are considered. Compared with the materials of oil and gas exploration and model representations of previous years about the geological structure of this territory. The resulting constructions have a high level of detail; this made it possible to revise many existing geological ideas about the prospects of oil and gas potential of the Verkhnelensky uplift.

Aim. The purpose of this work is a comprehensive analysis of the geological structure and prospects of oil and gas potential of natural reservoirs of the Vendian-Cambrian, including organogenic reservoirs of oil and gas in reef structures (biostromes) in the contour of positive structural forms above the protrusions of the crystalline basement, which were first identified by seismic exploration. 

Materials and methods. Under the extended shaft s, which were mapped earlier in the sedimentary cover along the halogen-carbonate thickness of the Lower Cambrian, local protrusions were found for the first time in the zones of projections of the axial parts on the surface of the heterogeneous crystalline basement according to high-precision seismic data. Earlier, over one of these protrusions, in the carbonate deposits of the Khristoforovsky horizon of the Lower Cambrian salt-bearing strata, the Znamenskoye (Balykhtinskoye) natural gas field was discovered by drilling. 

Results. Domed objects on the foundation surface, previously known only in the Atovo-Shamanov zone, are now isolated on the surface of a heterogeneous crystalline foundation within the axial parts of all major positive linear and brachianticlinal folded structures. On the northern side of the Kachugsky shaft in the deposits of the Litvintsevskaya and Angarskaya formations, in the southern side of the Zhigalovsky shaft in the Osinsky productive horizon, local pronounced domed objects with a flat base, with a sharp thickening in the core were recorded for the first time. It is suggested that in the Early Cambrian, in the axial part of the Verkholensky anticline uplift , Zhigalovsky and Kachugsky shaft s, there were conditions for the formation of biohermal structures similar to the studied biostromes of the Bozhekhansky shaft-like uplift. 

Conclusion. The connection of local positive structures (Balykhtinskaya, Typtinskaya, Znamenskaya) of the Zhigalovsky shaft and the protrusions of the foundation is documented for the first time. Above these local protrusions of the foundation, according to modern SRR data, objects with increased capacity are mapped in the intervals of known productive horizons, presumably bioherms or biostromes, which are recommended for study by drilling. On this basis, conceptions of the geological evolution of linear folding in the sedimentary brow of the Ilginckaya paleodepression are fundamentally changing. The tasks of the next stage of exploration include the study of the morphology of the protrusions of the foundation, detailing the structure of terrigenous deposits (the development of deposits of the Shaman productive horizon is expected by analogy with the Atovo-Shaman, Notai uplifts), detailing the structure of the Vendian Cambrian and Cambrian carbonate megareservoir. Organogenic reservoirs of oil and gas are expected in reef structures (biostromes) in the contour of positive structural forms above the protrusions. 

1. Adamov E.A., Tsobin V.A., Chechel E.I. Some features of the geological structure and development of the Ilga depression in connection with the prospects of potash. // Proceedings of the Institute of Geology and Geophysics of the SB Academy of Sciences of the USSR, 1970. — 116. — pp. 100–110.

2. Antsiferov A.S. Oil and gas potential of the Zhigalovsky shaft // Geology and oil and gas potential of Eastern Siberia. Moscow: Nedra, 1966. — 440 p.

3. Britan I.V., Zharkov M.A., Kavitsky M.L. et al. Structure and conditions of formation of Cambrian salt-bearing deposits on the territory of the USSR // Problems of salt accumulation. Vol. 2. Novosibirsk: Nauka, 1977. p

4. Vakhromeev A.G., Smirnov A.S., Mazukabzov A.M., Shutov G.Ya., Gorlov I.V., Misyurkeeva N.V., Ogibenin V.V. Verkhnelenskoe arch uplift — the main object of preparation of the resource base of the Irkutsk Gas Production Center // Geology and mineral resources of Siberia. — 2019. — No. 3. Nauka, pp. 38–56.

5. Vakhromeev A.G., Meisner A.L., Kolmakov A.V. et al. Mapping of the surface of the crystal foundation of the Verkhnelensky arch rise, Irkutsk Amphitheater, according to modern aerogeophysical survey // Geodynamic evolution of the lithosphere of the Central Asian Mobile Belt (from ocean to continent): Materials of the meeting. — Irkutsk: Institute of the Earth’s Crust SB RAS, 2021. — Issue 19. — pp. 27–30.

6. Vakhromeev A.G., Kornilova T.A., Misurkeeva N.V., Urenko R.S., Stanevich A.M., Stepanova N.I., Pulyaevskiy M.S. Bioherms of the Bozhekhan uplift in the Cis-Baikal trough as a marginal barrier reef system of a Cambrian salt basin of the southern Siberian platform. Earth sciences and subsoil use. 2022;45(3):246-264. (In Russ.)

7. Gaiduk A.V., Almendinger O.A. Conditions for the formation and criteria for forecasting zones of improved reservoir properties of ancient Vendian-Cambrian reservoirs // Scientific and Technical Bulletin of OJSC NK Rosneft. — No. 1-2013. — Vol. 30. - pp. 10–13.

8. Geology of oil and gas of the Siberian platform / Edited by A. E. Kontorovich, V. S. Surkov, A. A. Trofi muk. — Moscow: Nedra, 1981. — 552 p.

9. Gubina E.A., Tikhonova K.A., Vinokurova O.A., Lukyanov V.V., Volkov V.G., Neustroev K.A., Savichev K.S. Model of the Osinsky productive horizon (layer B1) at the fi elds of the Irkutsk region // Oil industry. — 2022. — No. 2. — pp. 46–51.

10. Dolnik T.A. Stromatolites and microphytolites in the Riphean and Vendian stratigraphy of the folded framing of the Siberian platform. Novosibirsk: NITSOIGGM SB RAS, 2000. — 320 p.

11. Zharkov M.A., Chechel E.I. Sedimentary formations of the Cambrian Angara-Lena trough. Novosibirsk: Nauka, 1973. — 238 p.

12. Zharkov M.A., Zamaraev S.M. History of tectonic development of the south of the Siberian platform // Questions of comparative tectonics of ancient platforms. Moscow: Nauka, 1964. — 156 p.

13. Zamaraev S.M. Regional structures of the southern part of the Siberian platform. Moscow: Nauka, 1967. — 247 p.

14. Zgirovsky N.Z. New data on the structure of the Akhinsky shaft according to seismic surveys // Materials on geology and geophysics of the Siberian platform. Issue 1. Vost-Sib. Book Publishing house, 1968. p. 159–164.

15. Dmitrievsky A.N., Samsonov Yu.V., Ilyukhin L.N. et al. Zones of oil and gas accumulation in carbonate deposits of the Siberian platform. Moscow: Nedra, 1993. — 158 p.

16. Dubrovin M.A. Salt tectonics of the Upper Lena depression of the Siberian platform. — Novosibirsk: Nauka, 1979, 95 p.

17. Karasev I.P., Karaseva V.I. Geological structure and oil and gas potential of the Irkutsk amphitheater.// Geology and oil and gas potential of Eastern Siberia. Moscow: Nedra, 1966. — 440 p.

18. Map of the deep structure: map of the diff erentiated granite-metamorphic layer (on the surface of the crystal foundation). Scale 1:1,000,000. N-48 (Irkutsk) / VSEGEI, Irkutskgeofi zika, IGE; comp. A. G. Pashkova. — 2010.

19. Karasev O.I. Morphology and basic genetic types of local uplift s of the south of the Siberian platform // Materials on geology and geophysics of the Siberian Platform. Irkutsk: Vostochno-Sib. Book publishing house, 1968. — 332 p.

20. Kalinkina L. I., Shutov G. Ya. Riphogenic deposits of the Srednemotskaya sub-formation of the Nepsky arch of the south of the Siberian platform // Soviet geology. — 1981. — No. 1., pp. 68–72.

21. Kvachko S.K., Gubina E.A., Tikhonova K.A., Belozerova O.S., Dudueva M.G. Structural and material complexes of the crystalline basement of the central part of the Nepsko-Botuobinskaya anteclise and their relationship with oil and gas // Geomodel. Collection of materials conf. — Irkutsk. — 2023. ISBN 978-5-9651-1410-8

22. Kitaeva I.A. Types and genesis of the fi ltration-reservoir space of reservoir rocks of the Lower Cambrian carbonate deposits of the southwestern slope of the Nepsko-Botuobinskaya anteclise. The author’s abstract for the academic competition. degrees of Candidate of Geological Sciences. Moscow, 2020. — 26 p.

23. Komarova N.I., Ilyin A.S., Shashin S.G. Types of carbonate reservoirs and criteria for their prediction in connection with the search for oil and gas deposits in the Cambrian sediments of the southern Siberian platform. // In the collection of geological conditions and methodological features of the search for oil and gas deposits on the Siberian platform. Tez. reports of the All-Union Scientifi c-Technical meetings on October 27–29, 1981. — Irkutsk. — 1981

24. Korolyuk I.K. Some Cambrian stromatolites of the Irkutsk amphitheater // Proceedings of the Institute of Oil of the USSR Academy of Sciences. — 1956. — Issue 7.

25. Korolyuk I.K. Comparative characteristics of the Riphean and Cambrian formations of the Baikal region. Moscow: Publishing House of the USSR Academy of Sciences, 1962. — 158 p.

26. Korolyuk I.K. Features of the structure of the shaft s of the southern part of the Baikal region on the example of the Bozhekhansky uplift // Tectonics of oil and gas bearing regions of Siberia. — Moscow: Nauka, 1967. — pp. 60–70.

27. Kononov A.I. Genetic types of local structures of the Irkutsk amphitheater. / Collection “Geological structure and oil and gas potential of the Irkutsk amphitheater”. Moscow: Gostoptehizdat, 1960.

28. Kuznetsov V.G., Ilyukhin L.N., Dmitrievsky S.A., etc. Ancient carbonate strata of Eastern Siberia and their oil and gas potential. Moscow: Scientifi c World, 2000. — 104 p.

29. Maksimova E.N., Chertina K.N. Cyclic structure of the Osinsky horizon on the example of one of the deposits of the Nepsko-Botuobinskaya anteclise // Lithology of sedimentary complexes of Eurasia and shelf areas. Materials of the IX All-Russian Lithological Meeting (with international participation). Kazan, 2019. — pp. 271–272.

30. Mandelbaum M.M. Geological structure and oil and gas potential of the zone of Upper Angara dislocations. In the collection: Geophysical studies and problems of oil and gas potential of the south of the Siberian platform. Issue 2. — Moscow, 1962. — pp. 3–108.

31. Melnikov N.V. Wend-Cambrian saline basin of the Siberian platform. (Stratigraphy, history of development). — Novosibirsk: Sniggims, 2018. — 177 p.

32. Methodological recommendations for a comprehensive assessment of carbonate reservoirs when calculating oil and gas reserves in the deposits of Eastern Siberia. // Shashin S.G. et al. Irkutsk: VostSibNIIGGiMS, 1990. — 114 p.

33. Myshevsky N.V. Ignyalinsky barrier reef — a new promising object on the Nepsky vault // Geology and Geophysics. — 1991. — No. 11. — pp. 99–107.

34. Stratigraphy of oil and gas basins of Siberia. Cambrian of the Siberian Platform: in 2 vols. Vol. 1: Stratigraphy / ed. by Yu.Ya. Shabanov. — Novosibirsk: INGG SB RAS, 2016. — 497 p.

35. The structure and history of the development of the Pre-Baikal foothill trough [Text] / S.M. Zamaraev, O.M. Adamenko, G.V. Ryazanov, [et al.]. A.A. Kulchitsky, R.S. Adamenko, N.M. Vikentieva. Moscow: Nauka, 1976. — 136 p.

36. Sukhov S.S. On the role of facial-sedimentological criteria in the reconstruction of Cambrian paleobassins of the East of the Siberian platform // Modern problems of sedimentology in oil and gas engineering: Proceedings of the III All-Russian Scientifi c and Practical Sedimentological Meeting (Tomsk, April 10–12, 2017). — Tomsk, publishing house of the CPPS ND, 2017. — pp. 209–214.

37. Titorenko T.N., Anisimova S.A., Anisimov A.Y. Paleontology of the Precambrian. Phytoliths (stromatolites and microphytolites): uch.-method. stipend. Irkutsk: Publishing House of the ISU, 2012. — 117 p.

38. Trufanova N.V., Krivoshchekov A.L., Naumova Yu.A. Methodology and results of kinematic interpretation according to the regional profi le “Kovyktinskoye deposit — Pre-Atomic defl ection” // Technologies of seismic exploration. — 2007. — No. 3. — pp. 83–91.

39. Chertina K.N., Maksimova E.N., Vilesov A.P., Krokhaleva O.A. Conceptual sedimentological model of patch reefs of the Osinsky horizon of the Srednebotuobinsky deposit (Nepsko-Botuobinskaya anteclise) // All-Russian lithological meeting “Geology of reefs”: conference materials. Tyumen, 2020. — pp. 1–30.

40. Chechel E.I., Mashovich Ya.G., Gilev Yu.G. Regularities of the structure of salt-bearing deposits of the Cambrian south of the Siberian platform. Moscow: Nedra, 1977. — 144 p.

41. Shutov G.Ya. Verkhnelenskoe arch uplift — a new promising object for the search for gas deposits in the Angara-Lena NGO / Geology of oil and gas. — 1987. — No. 1. — pp. 5–9.