Simulation of kerogen evolution by thermodynamic methods (on the example of Southern oil and gas region)

Abstract

The article considers the methods for estimating the level of organic matter transformation, scattered in sedimentary strata, in the process of catagenetic transformations. The authors show the efficiency of kerogen property research by coal petrographic methods and palynological analysis, the purpose of which is to establish the paleotemperature that was actualized in the process of evolution. The advantages and disadvantages of establishing the organic matter generation potential by pyrolytic methods, primarily by pyrolysis by Rock-Eval, are evaluated. In the context of the organic matter evolution indirect study methods, brief information on gas geochemistry is given and the main indicators used in the analysis of the chemical composition of gases in hydrocarbon deposits are listed. It is shown that the equilibrium thermodynamics apparatus can provide information about the conditions and level of organic compounds transformation in the lithosphere. The general information on geological history of the Southern oil and gas region of Ukraine is given and the main events that influenced the modes of transformation of organic matter are shown. The most important of these were the plate collision processes and the accompanying spreading that took place during the approaching of the Arabian continent and Eurasia, which led to the formation of a faults network: submeridional and sublatitudinal. According to the chemical composition of the region's depo-sits, graphs within the coordinates C2/C3 to C2/i-C4 and ln(C2/C3) to ln(C1/C2) are plotted. According to the graphs, the authors establish the trends of organic matter evolution: development in the direction of maturation and kerogen formation without secondary oil destruction. Information on the method of calculating the kerogen/gas system composition according to the Jaynes formalism is given. According to thermodynamic simulation combined with the chemical composition of deposits, maps of equilibrium temperatures and depths for several temperature flows are constructed. The effect of the individual deposits geological structure on the evolution of its contents is shown. The map of generation depletion of the region kerogen is made. According to the results of the map analysis, it is found that the kerogen of the Kerch-Taman interpericline depression is maximally depleted, while the kerogen of the southern side of the Karkinitsky-North-Crimean depression retains the high potential for the formation of light hydrocarbons.