Relationship of lithological data with the sedimentation environment of the Upper Batian deposits of the Kogalym region

Research subject. Upper Batian deposits (formation U2) of the Eastern part of the Kogalym region, within the North Nizhnevartovsk monocline. Aim. Reconstruction of the sedimentation environment of the U2 formation in the Kogalym region. Materials and methods. The reconstruction of sedimentation environments was conducted based on a macroscopic description of core samples with identification of structural and textural features of rocks from 35 wells. The clarification of sedimentation settings was carried out based on the description of 41 thin sections and a granulometric analysis of the clastic part of the studied rocks. Results. According to the macroscopic study, the U2 layer is composed of an uneven alternation of silty-argillaceous and silty-sandy rocks with coal interlayers. The rocks are of a polyfacial nature, represented by deposits of continental, transitional, and marine genesis. The thickness of the deposits varies markedly depending on the paleorelief of the area. The optical petrographic study revealed the polymictic composition of the studied rocks, which, according to the classification by V.D. Shutova, correspond to the arkose (graywacke arkose), less often graywacke (feldspar-quartz, quartz-feldspar greywackes) group. Cement most often exhibits a carbonate-clay composition. Rocks of marine genesis are characterized by a decrease in the proportion of rock fragments and an increase in the proportion of mechanically stable accessory minerals (zircon, garnet, tourmaline). The rocks of continental genesis are characterized by the maximum content of micas and plant detritus. An increase in the content of pyrite is noted in the sediments transitional from the continent to the sea. The grain-size analysis data of reservoir rocks of the U2 formation showed that both coastal-marine and channel deposits were formed in environments with active hydrodynamics of the medium, when the dynamic processing of clastic material exceeded the intensity of its supply. Conclusions. The performed lithofacies studies made it possible to reconstruct the sedimentation environment, as well as to reveal specific features in the distribution of the silty-sandy rock components of the U2 formation.

1. Alekseyev V.P., Fedorov Yu.N., Maslov A.V., Russkii V.I., Pecherkin M.F., Pudovkina M.A. (2007) The composition and genesis of the deposits of the Tyumen suite of the Shaim oil and gas region (Western Siberia). Ekaterinburg, UGGU, 209 р. (In Russ.)

2. Chernova O.S. (2004) Reservoir sedimentology. Tomsk, TPU, 453 p. (In Russ.)

3. Isayev G.D., Doroginitskaya L.M., Potryasov A.A., Skachek K.G. (2007) Evolution of the lithofacies model of the Jurassic productive complex of the Tevlinsko- Russkinskoye field. Ways to realize the oil and gas bearing and ore potential of KhMAO-Yugra. V. 1. Khanty-Mansiysk, Izdatnaukaservis, 344-353. (In Russ.)

4. Kontorovich A.E., Vakulenko L.G., Kazanenkov V.A., Popov A.Yu., Sayenko L.S., Topeshko V.A., Yan P.A. (2008) Paleogeography, conditions of accumulation of reservoirs, patterns of distribution of oil deposits in the U2 horizon (bat) of the central regions of the West Siberian basin. Lithological and geochemical foundations of the forecast of oil and gas potential: Collection of materials of the Int. sci.-pract. conf. St.Petersburg, VNIGRI, 329-336. (In Russ.)

5. Myasnikova G.P., Mukher A.G., Devyatov V.P. (2009) Paleogeography and sedimentation dynamics of the Jurassic of Western Siberia. Jurassic system of Russia: problems of stratigraphy and paleogeography. Scientific materials of the III All-Russian meeting. (Ed. by V.A. Zakharov). Saratov, Nauka Publ., 153-155. (In Russ.)

6. Overview map of the West Siberian oil and gas province on a scale of 1 : 2 000 000 (Maps). (1990) (Ed. by A.M. Brekhuntsov, I.I. Nesterov, V.I. Shpilman). Tyumen, ZapSib-NIGNI. (In Russ.)

7. Passega R. (1964) Grain size representation by CM patterns as a geological tool. J. Sed. Petrol., 34(4), 68-75.

8. Romanovskii S.I. (1977) Sedimentological foundations of lithology. Leningrad, Nedra Publ., 408 p. (In Russ.)

9. Rozhkov G.F. (1979) Granulometric maturity of sands. Litologiya i Polez. Iskopaemye, (5), 106-125. (In Russ.)

10. Rukhin L.B. (1947) Granulometric method for studying sands. Leningrad, LGU, 213 p. (In Russ.)

11. Sadykov M.R., Pecherkin M.F., Kuzʼmin Yu.A. (2007) Features of the geological structure of the Lower-Middle Jurassic deposits within the license areas of OOO “LUKOIL – Western Siberia”. Ways to realize the oil and gas bearing and ore potential of KhMAO-Yugra. V. 2. Khanty-Mansiysk, Izdatnaukaservis, 308-315. (In Russ.)

12. Shvanov V.N. (1987) Petrography of sandy rocks (component composition, taxonomy and description of mineral species). Leningrad, Nedra Publ., 269 p. (In Russ.)

13. Vakulenko L.G., Predtechenskaya Ye.A., Chernova L.S. (2003) Experience in the use of granulometric analysis for the reconstruction of the conditions for the formation of sandstones of the productive strata of the Vasyugan horizon (Western Siberia). Lithosphere (Russia), (3), 99-108. (In Russ.)