Stryzhak L. Lithogenesis and nature of reservoirs of deep-seated terrigenous deposits of the Lower Carboniferous of the central part of the Dnieper-Donetsk depression

The thesis is devoted to the study of lithogenesis processes and the establishment of the nature of hydrocarbon reservoirs of deep-lying terrigenous deposits of the Lower Carboniferous of the central part of the Dnieper-Donetsk Depression. It was proved that among the main: structural, paleogeographical, facial and paleotectonic criteria of oil and gas potential for the area of research of deep-laying secondary reservoirs the main processes are the processes of superimposed lithogenesis, namely fluid lithogenesis. On the basis of the established stage transformations, the features of lithogenesis processes were identified with an assessment of their influence on the formation of filtration-capacity properties of hydrocarbon reservoirs. The study of the lithogenesis of the central part of the Dnieper-Donetsk Depression also covers the problem of the formation of secondary gas-bearing reservoirs at greater depths. The deep-lying horizons Golotivshchinsko - Mekhedovsko - Lutsenkovsky - Sviridovskaya zone are characterized by a fractured-pore type of reservoir, and as one of the subtypes - internal grain porosity, which also plays an important role in the general type of porosity. The result of the superimposed lithogenetic and tectonic processes are secondary pores, caverns, cracks and suture-stylolite, which determine the filtration-capacity features of rocks in the study area. Studied secondary processes of lithogenesis of terrigenous reservoirs of productive horizons of the Srebnenskaya depression they are clearly divided into those promoting the development of void space and vice versa, which lead to even greater compaction of rocks. The features of the mineral composition, newly formed structures, changes in petrophysical parameters and other features of deep-lying terrigenous rocks of the Lower Carboniferous in the process of lithogenesis have been investigated. Revealed causal relationships between mineral new formations and reservoir properties of productive sandstones of deep-lying horizons of the Dnieper-Donetsk Depression. It was found that authigenic minerals were formed as a result of fluid lithogenesis in the "fluid-rock" system. A detailed lithogenetic analysis of all authigenic and detrital minerals as indicators of the stages of catagenesis was carried out, and the influence of each of them on the filtration-capacity properties of rocks was detected. A detailed lithogenetic analysis of all authigenic and detrital minerals of terrigenous rocks as indicators of the stages of catagenesis has been carried out and their influence on the filtration-capacity properties of rocks has been established. For the first time, for the central part of the Dnieper-Donets Depression, a quantitative assessment of the structural parameters (metamorphic coefficients and changes) of terrigenous reservoirs was carried out using different methods (method of O. Chernikov, S. Savkevich, O. Orlova) a comparative analysis of the results with palynological data and reflectance proprieties of vitrinite was made. The studied post-sedimentation processes of lithogenesis can improve the quality of forecasting the porosity-permeability properties of rocks when searching for hydrocarbon deposits in the central part of the Dnieper-Donetsk Depression. Key words: lithogenesis, lower Carboniferous deposits, Dnieper-Donetsk depression, reservoir, oil and gas potential.