| Summary: | The relevance of the discussed issue is caused by the fact that really all geological issues are solved on the basis of the models which accuracy increases considerably when using sedimentological component. Sedimentalogical factors control the conditions of formation, placement and quality of a reservoir and caps. It means that consideration of sedimentological models increases the efficiency of exploration for oil and gas, especially, preparation of deposits to development and development drilling. The main aim of the research is justification of importance of J1 a formation deposition (formed by sandstones of Upper Jurassic deposits) of T condensate field (Yamal-Nenets Autonomous District) according to the coredata performed on two wells. Research methods: Lithological composition analysis of the rocks, separation of rocks on lithological characteristics on lithotypes, facies analysis, complex analysis of lithological and petrophysical data. Results. Based on the coredata analysis the authors have selected six lithotypes and six sedimentary environments (facies) of deposits of J1 a. All lithotypes have different reservoir (permeability and porosity) properties. The lithofacies were grouped into larger sedimentary complexes - facies associations. Complex associations allocated within the T field of the studied formation allowed justifying the sedimentological model of deposit formation. Formation of J1 a sediment accumulated in the barrier-island environment complex from the west to the east. It is shown that lithotypes 3 and 4 have the best filtration-capacitive properties, and lithotype 1 has the worst quality. Litotiype 3 was formed in a Flood Tidal Delta marine and tidal inlet, deposits litotype 4 was formed in shallow-marine environment during transgression, influenced by moderate activity wave processes.
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