Hydrothermal Transformations of Organic Matter of Carbon-Rich Domanik Rock in Carbon Dioxide Environment at Different Temperatures

The influence of temperature on the nature of transformation of organic matter (OM) of carbon-rich rocks from Upper Devonian Semilukian–Mendymian (domanik) deposits of the Berezovskaya area of the Romashkino oilfield in hydrothermal processes has been studied. The experiments have been carried out at temperatures of 200, 250, 300, and 350°C in a CO 2 medium in the presence of water in an amount of 30% of rock mass in the reaction system. The yield and changes in the component, structural-group, and hydrocarbon-group composition of extracts obtained from rocks before and after hydrothermal experiments have been evaluated. It has been established that at temperatures of 300 and 350°C, high-molecular-weight components and insoluble kerogen undergo degradation processes, leading to a noticeable increase in the concentration of free hydrocarbons in the rock and their more complete extraction from the rocks. By the nature of molecular-mass distribution of normal and isoprenoid alkanes, the extracts from the rocks are similar to oils of the A 1 and A 2 types (according to the chemical classification by A.A. Petrov) from productive formations of the Devonian and Carboniferous deposits of the Romashkino field. The treatment of the domanik rock at lower temperatures of 200 and 250°C facilitates more intensive recovery of free hydrocarbons from the rock, without significantly affecting the structure of kerogen by destructive processes. The influence of temperature on the phase transformations of asphaltenes and their paramagnetic properties, as well as on the composition of biomarker hydrocarbons associated with the genotype of original OM and lithology and maturity of possible oil producing strata, has been revealed. It has been shown that carbonate–siliceous source rocks of domanik deposits of the Romashkino field can become an additional source of petroleum hydrocarbons in the case of development using hydrothermal technologies.