The analysis was undertaken to unravel possible reasons of reservoirs separation in hydrocarbon accumulations. Separation zones are practically not recognized by direct evidence such as well correlation, or seismic data. Possible locations of such separation zones can be inferred only from the presence of a combination of indirect indicators including: multi-facies zones, contact of sedimentary bodies from different depositional source areas, zones of reduced net thickness or NTG, increased compartmentalization, continuity, lack of communication between injecting and producing wells, contradictory well test results, different hydrocarbon contacts. The paper considers main reasons of forming the zones of separated reservoirs, which can be associated with a junction of areas formed by different depositional centers, or with reduced NTG of sedimentary sequences separating major sand depositional features, with boundaries of facies where pore space structure may change, with capillary barriers. Separation of reservoirs in the same formation zone can also be confirmed by a different reservoir temperature (when excluding reservoir production effects), presence of faults including “rootless” faults such as, for instance, a clastic elongated dike filled with clastic material. Besides, influence can be exerted by geochemical processes, as well as by lithology change and porosity reduction at facies boundaries, or by interfacing with thin shale barriers. As a result of the analysis, the authors identified main reasons of reservoirs separation in hydrocarbon accumulations
References
1. Metodicheskie rekomendatsii po podschetu zapasov nefti i gaza ob’emnym metodom. Otsenka kharaktera nasyshchennosti po dannym GIS (Guidelines for the calculation of reserves of oil and gas by volumetric method. Assessment of the nature of saturation according to well logging): edited by Petersil’e V.I., Poroskun V.I., Yatsenko G.G., Moscow – Tver: Publ. of VNIGNI, 2003, 258 p.
2. Smirnova E.V., Azarova N.O., Utyashev Yu.N. et al., Problems solution of oil and gas deposits geometrization of the Aptian-Albian age in the north-east of the West Siberia (In Russ.), Geologiya, geofizika i razrabotka neftyanykh i gazovykh mestorozhdeniy, 2019, no. 8, pp. 4-10, DOI: https://doi.org/10.30713/2413-5011-2019-8(332)-4-10
3. Polishchuk A.V., Sidorov A.E., Nassonova N.V. et al., Conceptual sedimentation model as the basis of geological correlation in a case study of AT6-8 reservoirs of Beregovoye field in West Siberia (In Russ.), Izvestiya vysshikh uchebnykh zavedeniy. Neft’ i gaz, 2022, no. 3, pp. 23-37, DOI: https://doi.org/10.31660/0445-0108-2022-3-23-37
4. Nassonova N.V., Distanova L.R., Kalabin A.A., Devyatka N.P., Regional and local factors of cracking formation in clay-silicon deposits of the Nizhneberezovskaya subsuite (In Russ.), Geologiya, geofizika i razrabotka neftyanykh i gazovykh mestorozhdeniy, 2020, no. 1, pp. 19-25, DOI: https://doi.org/10.30713/2413-5011-2020-1(337)-19-25
5. Bol’shakov Yu.Ya., Dinamicheskoe modelirovanie zalezhey nefti i gaza: Kurs lektsiy (Dynamic modeling of oil and gas reservoirs: Course of lectures), Tyumen: Publ. of Tyumen State Oil and Gas University, 2003, 66 p.
6. Dahlberg E.C., Applied hydrodynamics in petroleum exploration, Springer-Verlag New York, Inc. 1995, 296 p.
7. Strakhov N.M., Osnovy teorii litogeneza (Basics of the theory of lithogenesis). Part 1. Tipy litogeneza i ikh razmeshchenie na poverkhnosti Zemli (Types of lithogenesis and their placement on the Earth’s surface), Moscow: Publ. of USSR AS, 1960, 212 p.
8. Danenberg E.E., Belozerov V.B., Brylina N.A., Geologicheskoe stroenie i neftegazonosnost’ verkhneyursko-nizhnemelovykh otlozheniy yugo-vostoka Zapadno-Sibirskoy plity (Tomskaya oblast’) (Geological structure and oil and gas potential of Upper Jurassic-Lower Cretaceous deposits in the southeast of the West Siberian plate (Tomsk region)), Tomsk: Publ. of TPU, 2006, 207 p.
9. Nedolivko N.M., Evolution of void-pore space in oil-water contact zones (In Russ.), Izvestiya Tomskogo politekhnicheskogo universiteta, 2010, V. 316, no. 1, pp. 99-107.
10. Zhukovskaya E.A., Vakulenko L.G., Yan P.A., Oksfordskiy konkretsienosnyy gorizont v osadochnykh basseynakh. Yurskaya sistema Rossii: problemy stratigrafii i paleogeografii (Oxford nodule horizon in sedimentary basins. Jurassic system of Russia: problems of stratigraphy and paleogeography), V All-Russian meeting: scientific materials, Ekaterinburg: IzdatNaukaServis Publ., 2013, 270 p.