To estimate reserves and optimize the development of hard-to-recover hydrocarbons from Middle-Upper Jurassic deposits reliable information on the ownership of the reservoir to certain strtonum is necessary. The question of the dismemberment of the hydrocarbon deposits Naunak and Tyumen suite in the South-East of Western Siberia is still controversial.
Material for study is based on samples from core 7 wells: No. 1, 2, 5 (Dvoinoye field) and No. 446, 170, 430, 301 (Snezhnoye field). The relevance of research is caused by necessity of using the results to update the geological model, calculation of the declared reserves of hydrocarbons and to optimize development of the hard deposits on the Dvoinoye and Snezhnoye fields. Guide fossils for the Tyumen suite (Tomsk phyto-horizon) are the ferns (Coniopteris vialovae, Raphaelia diamensis); czekanowskiales (Czekanowskia irkutensis, Cz. rigida, and Phoenicopsis mogutchevae); equisetaceous plants (Equisetites lateralis). The guiding forms for Naunak suite (Naunak phyto-horizon) in the studied wells are czekanowskiales Czekanowskia tomskiensis. Productive deposits of the Tyumen suite are characterized by a high degree of heterogeneity, lithological variability, with predominance of more interlayers of mixed breeds (are sandstones are mudstones). According to hydrolysate module values Tyumen suite is composed of continental sediments with the participation of products redeposition weathering and Naunak suite, with a reduced value of the modulus is composed of terrigenous rocks with the participation of volcanic-clastic material. Titanium module values show that Tyumen suite formed in the semi-arid climate. On the background of the prevailing semi-arid conditions at the end of the middle Jurassic era in the study area there were episodes of humidity.
An integrated lithogeochemical, biostratigraphic and facies studies allowed to carry out the dismemberment of the Middle-Upper Jurassic sediments in the studied sections and to clarify the boundary between Naunak and Tyumen suite, as well as to separate deposits of different genesis: the inland waterways (Tyumen suite) and coastal plains, occasionally flooded by sea.
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