Kerogen maturity variability in Domanik high-carbonaceous formation in the central Volga-Ural petroleum basin

UDK: 550.8:553.98(470.41) + 553.98.061.32

DOI: 10.24887/0028-2448-2026-7-6-11

Key words: Domanik high-carbonaceous formation, catagenesis, Volga-Ural petroleum basin, oil-source rock, hard-to-recover reserves, kerogen transformation criteria

Authors: R.R. Abusalimova (TatNIPIneft, RF, Almetyevsk); А.F. Safarov (TatNIPIneft, RF, Almetyevsk); S.А. Vakhrameev (TatNIPIneft, RF, Almetyevsk); R.R. Аflyatunov (TATNEFT PJSC, RF, Almetyevsk); N.А. Nazimov (TATNEFT PJSC, RF, Almetyevsk); Т.V. Grigorenko (Lomonosov Moscow State University, RF, Moscow); А.G. Каlmykov (Lomonosov Moscow State University, RF, Moscow); G.А. Каlmykov (Lomonosov Moscow State University, RF, Moscow)

The Domanik high-carbonaceous formation rocks in the South Tatar Arch and the Melekess Depression of the Volga-Ural petroleum basin are traditionally regarded as the oil-source rocks that have either not yet entered the oil window or are at its very beginning. Analysis of the laboratory data over the recent years revealed that on the northern flank and in the central part of the South Tatar Arch, there are zones with significantly transformed kerogen. After hexane extraction of samples exhibiting a high degree of kerogen maturity, porosity values reach 6–10 %, allowing the Domanik deposits to be classified as promising unconventional reservoirs containing hard-to-recover reserves. These zones are confined to a sub-lateral belt near the northern boundary of the South Tatar Arch, to the western part of the central South Tatar Arch along the Altunino-Shunak depression, as well as to several local areas. The most probable reason for the presence of local zones with increased maturity is additional thermal heating, which could occur in areas characterized by numerous disjunctive faults during tectonic reactivation in the Carboniferous-Permian or later periods. However, presence of faults cannot be considered as the exclusive criterion for distinguishing intervals characterized by a high catagenetic maturity of Domanik organic matter. Exploration programs aimed at identification of hydrocarbon accumulations in Domanik formations should be based both on location of areas rich in organic matter and reconstruction of the tectonic history, including initiation and subsequent development of disjunctive faults.

References

1. Stupakova A.V., Fadeev N.P., Korobova N.I. et al., Criteria for oil and gas search in Domanic deposits of the Volga-Ural basin (In Russ.), Georesursy, 2015, no. 2(61),

pp. 77–86.

2. Safarov A.F., Aflyatunov R.R., Lutfullin A.A. et al., Evaluation of the resource potential of high-carbon rocks of the Saraylin series within the southeastern slope of North Tatar arch in the Republic of Tatarstan (In Russ.), Georesursy, 2025, V. 27, No. 2, pp. 243–254, DOI: https://doi.org/10.18599/grs.2025.2.18

3. Mel’nikov P.N., Varlamov A.I., Fortunatova N.K. et al., Results of quantitative estimation of unconventional oil resources of the Russian Federation (In Russ.), Geologiya i geofizika, 2024, V. 65, No. 1, pp. 8–25, DOI: https://doi.org/10.15372/GiG2023189

4. Bazhenova T.K., HC resources estimation of bituminous formations of Russian oil and gas bearing basins (In Russ.), Geologiya nefti i gaza, 2017, No. 5, pp. 37–50.

5. Varlamov A.I., Mel’nikov P.N., Poroskun V.I. et al., Unconventional oil reservoirs in high-carbon carbonate-siliceous Domanik formations, Volga-Urals Province: Results of studies and future development trends (In Russ.), Geologiya nefti i gaza, 2020, No. 6, pp. 33–52, DOI: https://doi.org/10.31087/0016-7894-2020-6-33-52

6. Tissot B.P., Welte D.H., Petroleum formation and occurrence, Springer-Verlag Telos, 1984, 699 p.

7. Tsarev V.V., Poroskun V.I., Geologicheskoe stroenie neftyanykh slantsevykh formatsiy zarubezhnykh stran (Geological structure of oil shale formations in foreign countries), edited by Varlamov A.I., Mel’nikov P.N., Moscow: Publ. of VNIGNI, 2022, 215 p.

8. Storozhenko V.D., Gazeeva F.M., Mingazutdinov A.N., Kuznetsov N.S., Kharakteristiki organicheskogo veshchestva domanikovoy vysokouglerodistoy formatsii na territorii Respubliki Tatarstan (Characteristics of organic matter of the Domanik high-carbon formation in the Republic of Tatarstan), Proceedings of TatNIPIneft’ / Tatneft’, Naberezhnye Chelny: Ekspozitsiya Neft’ Gaz Publ., 2025, V. 93, pp. 56–66.

9. Varlamov A.I., Petersil’e V.I., Poroskun V.I. et al., Technique of oil reserves estimation in Domanik deposits (In Russ.), Geologiya nefti i gaza, 2017, No. 5, pp. 51–65.

10. Galimov E.M., Is the source of hydrocarbons at the supergiant Romashkino oil field (Tatarstan) an influx from a crystalline basement or oil source sedimentary deposits? (In Russ.), Geokhimiya, 2015, No. 2, pp. 103–122, DOI: https://doi.org/10.7868/S001675251502003X

11. GOST 12113-94. Brown coals, hard coals, anthracites, solid dispersed organic matters and carbon materials. Method lor determination of reflectance Indices.

12. Jacob H., Classification, structure, genesis and practical importance of natural solid oil bitumen (“migrabitumen”), International Journal of Coal Geology, 1989, V. 11,

pp. 65–79, DOI: https://doi.org/10.1016/0166-5162(89)90113-4

13. Grigorenko T.V., Savostin G.G., Kalmykov A.G. et al., Domanic oil shale sediments organic matter and saturating fluids characteristics on the territory of the Tatarstan Republic (In Russ.), Georesursy, 2025, V. 27, No. 1, pp. 221–235, DOI: https://doi.org/10.18599/grs.2025.1.25

14. Khisamov R.S., Voytovich E.D., Liberman V.B. et al., Tektonicheskoe i neftegeologicheskoe rayonirovanie territorii Tatarstana (Tectonic and oil zoning of Tatarstan): edited by Khisamov R.S., Kazan’: FEN Publ., 2006, 328 p.

15. Gatiyatullin N.S., Baratov A.R., Liberman V.B., Oil bearing resources of Tatarstan in terms of the hypothesis of the earth degassing (In Russ.), Georesursy, 2013,

No. 1(51), pp. 17–22.