Hydrogeological aspects of the genesis, migration and forming of hydrocarbon fields in thе southern part of the Pre-Black Sea aquiferous basin

The model of forming of hydrocarbon deposits in the aquatic part of the Pre-Black Sea aquiferous basin substantiates by the set of hydrogeochemical, gas-geochemical, geotemperature, and hydrodynamic data. The model is based on modern views on the geodynamic history of development and makes it possible to state that the formation of gas-vapour systems occurred in the lower reaches of the sedimentary stratum of the riftogen at high pressures and temperatures and the presence of water. The basis of gas-vapour systems was both thermocatalytic and subcrustal (mantle) gases. Active heat and mass transfer of fluids during Alpine tectonogenesis continues to this day, which is confirmed by geothermal anomalies caused by the upward discharge of groundwater, endogenous gases – methane, helium, carbon dioxide, hydrogen, etc. The probable migration paths are sublatitudinal disjunctive dislocations and decompression zones in areas where tensile forces were manifested against the background of regional compression, for example, in places where faults of different directions intersect. As a result of gas migration, especially through clayey rocks, sorption of heavy hydrocarbons occurred, which determined gas-geochemical zoning. Gas migration was realized in a free high-temperature gas-vapour phase, which filled the traps, displacing or compressing the formation water. Active heat and mass transfer affects to the hydro- and gas-hydrogeochemical zoning and the filling of existing traps with hydrocarbons. Practical significance. Hydrogeochemical features such as water-dissolved gases and condensation water are the direct indicators of oil and gas potential. Hydrogeological model can be used to forecast deposits in other oil and gas-bearing regions (in particular, the Carpathian Foredeep).