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The paper presents approaches to characterization of shale source rocks using geochemical data for the case of the Bazhenov petroleum system in West Siberia. Regional patterns of oil distribution in the Bazhenov shale are shown to depend on their original total organic carbon (TOC) content and thermal maturity. The existing thermal maturity model for the Bazhenov Formation based on vitrinite reflectance (R° t ) of nearby beds has been updated using parameters measured by Rock-Eval pyrolysis ( T max, HI, PC, and RC) for the shale itself. The results were used to quantify hydrocarbon resources in different maturity zones. The relationship between TOC and the presence of para-autochthonous oil found for logged zones in the Bazhenov section allows allocating and quantifying oil resources in unlogged beds. [ABSTRACT FROM AUTHOR]

Abstract: This study provides a comprehensive sedimentologic analysis of the J2 prospective horizon (Middle–Late Bathonian) in the central West Siberian Basin. Based on the extensive dataset, it was established that structural complexity of this horizon is largely caused by a variety of depositional environments. Sedimentary facies of this horizon pass upward from widespread continental at the base, through deltaic or coastal-continental, to marginal-marine at the top. Change in the paleohypsometry of the study area reflects the distribution of depositional environments, in terms of the proportions of continental, transitional, and marine deposits. The study also shows that facies variability and change in depositional settings can have a significant control on reservoir quality, as well as its vertical and lateral distribution. Using a combination of detailed GDE reconstructions, structure contour mapping on the top and base of the J2 horizon, analyses of well test data, probability of reservoir presence, distribution of average porosity and permeability within different subenvironments, a composite map showing variations in the reservoir effectiveness in the J2 horizon was generated. [Copyright &y& Elsevier]