Obolon astrobleme: forward and inverse 3d geomodelling with the aim to resolve the question of hydrocarbon evidence

The relevance of studying unconventional prospects with oil and gas potential caused by extreme need to provide own resources of hydrocarbons in Ukraine. It should be noted that in one of the most promising oil-and-gas bearing regions in Ukraine (Dnieper-Donets depression) growth of hydrocarbon reserves by means of discovering new conventional deposits is very limited. Large number of Ukrainian geoscientists and experts believe that perspectives of discovering new oil and gas deposits here are associated with impact structures, called astroblemes. Hydrocarbon accumulations are known in several impact structures. About 50% of discovered impact structures within oil-and-gas bearing sedimentary basins in North America contain economically recoverable resources of oil and/or gas. There are seven known astroblemes in Ukraine and the most interesting one in terms of hydrocarbon potential is Obolon astroblem which is located in the southern near-flank zone of Dnieper-Donets depression. The purpose of presented research was to create a spatial geological and geophysical model of deep geological structure for the territory of Obolon astrobleme with the aim of defining hydrocarbon potential. The modelling technology was specified by the complexity of geological structure and lack of geological information about the astrobleme. It is based on using the method of joint geophysical inversion involving seismic data, gravimetric data, well logs and other geological information. The investigated territory is covered by geological, geophysical and geochemical surveys of different years. Significant amount of diverse geological and geophysical information defined the possibility to search for unconventional oil-and-gas promising prospects within Obolon astrobleme, basing on the accurate study its geological structure using the “Technology of integral interpretation complexgeological and geophysical data for oil and gas exploration”. The results of analyzing geodensity properties of created spatial geological-and-geophysical model of Obolon astrobleme together with favorable structural conditions ensured prediction of zones of sediments with improved reservoir properties within the main structural-lithological formations within the astrobleme. The scientific novelty of results is studying the distribution of geodensity properties of rocks within different stratigraphic formations, including the crystalline basement, in the territory of Obolon astrobleme. The practical significance of results is to define the priority prospects for exploration drilling, including ones which are potentially hydrocarbon-saturated within the crater, marginal swell and coptogenic complex of Obolon astrobleme.