Georesursy (May 2017)
Return to the catagenesis assessment of the sedimentary stratum in the Timan‑Pechora oil and gas basin by means of coal petrographical methods
Abstract
The Timan-Pechora basin still has a large importance and as a potential region for the hydrocarbons mining in Russia. At present, new facts are emerging from oil and gas exploration. The authors studied more than 50 samples from 11 wells. Most samples in this series were related to the Middle-Late-Frasnian sediments (Late Devonian), which are allocated in «domanic» horizon. Organic macerals of the studed samples are represented both by fragments of humic macerals and sapropelic OM (formed from algal material). The common organic macerals in Timan-Pechora basin are bituminites. They were met in all samples without exception and provide total content of OM,% in the rock. Bituminites are regularly distributed among mineral matter and color the rock in gray or more dark colors. Bituminite was used to determine the reflectance index (RB,%) that later was converted into the corresponding equivalent of vitrinite reflectance index (RVeq,%). This is particularly important as authors’ information was used together with the results of earlier studies. ID-modeling has been made in the program PetroMod (2015.1 Schlumberger) and helped to understand evolution in Timan-Pechora basin and maturity degree of rocks. The concept of the model was coordinated with the main evolution stages of the northeast European Platform and the foredeep Ural trough. The thicknesses of catagenesis zones and position of boundaries between them are indicators of thermal regime in the analyzed regions. The heat flow used in the modelling was one and the same for most tectonic regions (except foredeep Ural trough and Khoreiverskaja depression). According to the classification of the sedimentary basins by P. Robert (1985), 5 regions belong to regions with a normal or slightly hypothermal geothermal regime (heat flow 45-65 mV/m2) and foredeep Ural trough with heat flow up to 74 mV/m2 is a region with a high hyperthermal regime.
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