Secondary dolomitization of the Domanik black shales as an indicator of gas-water hydrocarbon-containing fluids upward migration in the Tatarstan territory

Abstract

© 2020 IOP Publishing Ltd. All rights reserved. The share of unconventional oil reserves is high in Russia and Volga-Ural region, including shale oil reservoirs. It contains around 65% of the total volume of hydrocarbon reserves in region, according to various data. Shale hydrocarbons are widely used in Russia. The main part of the Domaniki oil black shale is confined to carbonate-siliceous carbonaceous complexes of the Domanik horizon of the Francian stage of the Upper Devonian system. According to previous studies in the Domanik formation sedimentary complexes of the Volga-Ural oil and gas province, two types of rocks are distinguished - the Domanikites themselves and Domanikoids. Domanikites contain from 5 to 20% organic matter. Both types of carbonaceous rocks have a practically similar lithological composition. The difference between them lies in variations in siliceous component content and number of authigenic minerals. If content of very fine-grained silica was determined by primary sedimentation factors, then authigenic minerals are indicators of secondary lithogenesis processes. In this work, an attempt is made to compare organic matter content with dolomite mineralization, which is an active agent in mineral formation.