Bazhenov formation is the main source rock in Western Siberia. The large volume of accumulated regional seismic and geological data confirm the results of drilling, is a good basis for basin modeling the processes of generation, migration and accumulation of oil, formed by these source rocks. However, in addition to seismic and geological information required for the successful simulation a set of correct geochemical data. The most important geochemical parameters for basin modeling are the amount and type of organic matter and transformation ratio of the initial generation potential.
TomskNIPIneft JSC for many years performs systematic studies of rocks Bazhenov Formation. Rock samples (core, cuttings) from more than 700 wells of various regions of Western Siberia have been studied. The result of these studies was the experience on the justification of geochemical parameters needed to assess the volume of oil formation and basin modeling of oil generation rocks Bazhenov formation.
For Upper Jurassic - Lower Cretaceous source rocks suggested the selection of the section of the ‘classical’ Bazhenov formation, which is characterized by the results of pyrolysis Rock-Eval consistently high values of the parameter HI and low values of the parameter OI. The whole complex of geochemical parameters (pyrolytic, molecular, isotopic) characterizes this range consistently reducing conditions of sedimentation, which corresponds to the maximum of transgression, during which accumulated bituminous rocks Bazhenov horizon. The definition in the general section of the Bazhenov Formation and its stratigraphic analogues of this part of the section makes it possible to carry out the regional correlation of the geochemical parameters reflecting the patterns of change in conditions of sedimentation of organic matter of rocks Bazhenov horizon.
To assess the initial generation potential of organic matter HIo for the interval of ‘classical’ Bazhenov Formation justified its regular regional variations reflecting the change of the depositional environment. HIo mainly determined by the conditions of aerobic or anaerobic conversion of biomass source, therefore suggested the use of molecular parameters (Pr/Ph and 4MDBT/Phen), which have no apparent depending on katagenesis for Bazhenov Formation rocks.
In addition to differences in the source of generation potential of organic matter, its content, the molecular composition of the extracts were detected differences in the kinetics of thermal decomposition of kerogen. Variations of kinetic parameters can be traced not only in the territory of Western Siberia, but also in the section of the Bazhenov Formation within the individual wells. It was found that in its kinetic parameters and generation potential of the organic matter of the Bazhenov Formation is represented mainly by intermediate forms between types I and II kerogen and kerogen type II. However, sometimes there are small seams that contain kerogen type I.
Using the obtained geochemical data based scheme of the generation potential of Bazhenov formation rocks that reflects facies conditions of sedimentation of organic matter and the level of its katagenesis. We revealed cases when at a distance of 20 km oil generation rocks Bazhenov Formation changes several times.
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