The paper provides general information on the gas content and productivity of low-permeable gas reservoirs of the Berezovskaya formation. The Berezovskaya reservoir testing practices in directional and horizontal wells at the fields of Rosneft and Gazprom companies are described. The paper also considers the procedure of cased wells testing in the Berezovskaya formation developed to improve the operational success taking into account the unique properties of the target. The productivity of terrigenous reservoirs of the Upper Berezovskaya sub-formation depends on the rock grain size, the higher the grain size, the higher the reservoir quality and thus the gas rates. Commercial gas rates can be achieved even without hydraulic fracturing. The productivity of clay silicites of the Lower Berezovskaya sub-formation is an order of magnitude lower. The reservoir quality is defined by the pore space structure, the pore size, and the presence of natural rock fracturing. The best reservoirs are characterized by needle-shaped pore space and pore size of 200–500 nm. In fields with spongy pore space and pore size of up to 60 nm, formation tests without hydraulic fracturing were unsuccessful. Increased gas rates were obtained in wells located near tectonic faults (here is the maximum fracturing intensity), in tentative corridors above strike-slip faults, and at structural inflections. Hydraulic fracturing in silicite reservoirs provides a 3,8 to 47 times increase in gas rates reaching post-fracturing rates proportionate to the terrigenous reservoir of the Upper Berezovskaya sub-formation. The productivity potential of the Berezovskaya reservoir, based on the results of hydraulic fracturing tests in directional wells, amounted to up to 90 thousand m3/day. The economic efficiency of the Lower Berezovskaya sub-formation development can be achieved by drilling horizontal wells with multistage hydraulic fracturing. The initial rates of horizontal wells with multi-stage hydraulic fracturing reach up to 170 thousand m3/day. The well test results show the advantages of horizontal wells drilled across the maximum stress. The lessons learned by companies in studying and testing the Berezovskaya reservoir are insufficient for making decisions on the involvement of reserves into full-scale development. The production potential should be further investigated through pilot projects involving various well designs in areas with various types of natural fracturing.
References
1. Agalakov S.E., Bakuev O.V., New objects of hydrocarbon prospecting in over-Cenomanian deposits of the Western Sibiria (In Russ.), Geologiya nefti i gaza, 1992, no. 11.
2. Cherdantsev S.G., Nesterov I.I., Ognev D.A. et al., Stratigraphy and indexation of productive strata of the supra-Cenomanian gas-bearing complex of Western Siberia (In Russ.), Gornye vedomosti, 2017, no. 2, pp. 14–27.
3. Cherepanov V.V., Pyatnitskiy Yu.I., Khabibullin D.Ya. et al., Perspektivy narashchivaniya resursnoy bazy gazovykh mestorozhdeniy na pozdney stadii razrabotki putem izucheniya promyshlennogo potentsiala netraditsionnykh kollektorov nadsenomanskikh otlozheniy (Prospects for increasing the resource base of gas fields at a late stage of development by studying the industrial potential of unconventional reservoirs of supra-Cenomanian deposits), Collected papers “Trudnoizvlekaemye i netraditsionnye zapasy uglevodorodov: opyt i prognozy” (Hard-to-recover and unconventional hydrocarbon reserves: experience and forecasts), Proceedings of International scientific and practical conference, Kazan’: FEN Publ., 2014, pp. 104–110.
4. Cherepanov V.V., Men’shikov S.N., Varyagov S.A. et al., Problems relating to estimation of oil and gas potential of nizhneberezovsky sub-suite in the north of the Western Siberia (In Russ.), Geologiya, geofizika i razrabotka neftyanykh i gazovykh mestorozhdeniy, 2015, no. 2, pp. 11–26.
5. Vremennye metodicheskie rekomendatsii po podschetu zapasov gaza v zalezhakh berezovskoy svity i ee analogov v predelakh Zapadno-Sibirskoy neftegazonosnoy provintsii (Temporary methodological recommendations for calculating gas reserves in deposits of the Berezovsky formation and its analogues within the West Siberian oil and gas province), URL: https://gkz-rf.ru/ets/metodiki#page-accord-809.
6. Nassonova N.V. et al., Lithological and mineralogical heterogeneity of lower Berezovskian subseries of Medvezhye and Kharampurskoye fields (In Russ.) Neftyanaya provintsiya, 2021, no. 4-1(28), pp. 1–21.
7. Marinov V.A. et al., Upper cretaceous Berezovian regional substage of West Siberia (In Russ.), Byulleten’ moskovskogo obshchestva ispytateley prirody, 2023, V. 97, no. 4, pp. 12–39.
8. Distanova L.R., Nassonova N.V., Kudamanov A.I., Geological structure and gas potential of Campanian Verkhneberezovsky member by the example of one West Siberian field (In Russ.), Geologiya nefti i gaza, 2022, no. 5, pp. 5–16, DOI: https://doi.org/10.31087/0016-7894-2022-5-5-16
9. Abramov T.A. et al., Analysis of pressure transient test results for Beryozovskaya suite (In Russ.), Neftyanaya provintsiya, 2019, no. 4, pp. 234–247.
10. Kalabin A.A. et al., Fracturing of siliceous clayey rocks of the nb1 formation of the Berezovskaya suite in the central part of Western Siberia (In Russ.), Ekspozitsiya Neft’ Gaz, 2021, no. 1, pp. 24–27. DOI: https://doi.org/10.24412/2076-6785-2021-1-24-27.
11. Oshnyakov I.O. et al., Multiscale digital core analyses on unconventional argillaceous-siliceous rocks of Berezovskaya suite (In Russ.), Karotazhnik, 2022, no. 6(320), pp. 141–153.
12. Shklover V.Ya., Artemov N.A. Maryasev, I.G. et al., Opyt sozdaniya bazy dannykh po izucheniyu mikro- i nanometrovogo pustotnogo prostranstva kollektorov v tekhnologii “Tsifrovoy kern” (Experience in creating a database for studying the micro- and nanometer void space of reservoirs using the “Digital Core” technology), Collected paper “Informatsionnye sistemy i tekhnologii v geologii i neftegazodobyche” (Information systems and technologies in geology and oil and gas production), Proceedings of international scientific and practical seminar, 14–15 November 2019, Tyumen: Publ. of TIU, 2020, pp. 31–43.
13. Doroshenko A.A., Karymova Ya.O., Properties of voids in the Senonian gaize of the northern part of West Siberia (In Russ.), Ekspozitsiya Neft’ Gaz, 2017, no. 6(69), pp. 23–27.
14. Karymova Ya.O., Treshchinovatost’ opok senona severa Zapadnoy Sibiri (Fractures of Senonian flasks in the north of Western Siberia), Proceedings of XI scientific-practical conference of young scientists and specialists “Salmanovskie chteniya” (Salman’s readings), 30–31 March 2017, Tyumen’: Publ. of SibNATS, 2017, pp. 88–93.