Starodubets K. Development of prediction-search criteria for hydrocarbon deposits in the crystalline basement of the Dnipro-Donets depression on the example of the Yuliivsko-Skvortsivskyi test site.

The dissertation is devoted to the development of predictive-search criteria of hydrocarbon deposits in the crystalline foundation of the Northern bord of the Dnipro-Donets depression on the example of the Yuliivsko-Skvortsivsky polygon. The geological structure of the Nothern board of the Dnipro-Donets depression was investigated by many scientific and industrial organizations using deep drilling data, seismic survey materials and remote survey methods. The number of structural and geological constructions of the Northern board of DDD were accomplished and proposed a number of approaches to the formation of hydrocarbon fields in the region. However, moving to local objects where the aim is prospecting and exploration drilling, geologists face a complex small block structure, which is displayed on seismic maps incorrectly, according to the results of geophysical researches, consequently difficulties with the correct placement of wells and the probability of new industrial discoveries decreases. According to the modern schemes of tectonic zoning of the Northern board the area of works is located in the central part of the Kharkiv block , which is an integral part of the transverse Dnipro-Kurskyi (Kursko-Serednodniprovskyi) megablock of the Sarmatian shield foundation. The structural feature of this part of DDD board is determined by the Kharkiv ledge, which complicates the general monoclinic slope surface foundation of the board towards the Dnipro graben and (less noticeable) from the northwest to the southeast. The meridional deep faults in modern tectonic schemes play the main role to the transverse zonation of the Northern board of DDD. Among them there are Kryvorizko-Krupetskyi and Orikhovo-Kharkivskyi inter-megablock suture zones and subparallel interblock zones, in particular, Tsarychansko-Pysarivskyi separates the Kharkiv block from Sumy block. Due to the structural dependence of explosive traps on discontinuous dislocations, the analysis of the general patterns of fault-block tectonics and determining the structural position of potential explosive HC traps is of particular importance. At present, there is no single point of view concerning the processes that lead to the formation of hydrocarbons. Most researchers offer three approaches to resolve this issue: inorganic, organic and mixed (organic-inorganic approach). To evaluate the hydrocarbon potential of the prospective structures at Yuliivsko-Skvortsivskyi polygon, a complex express method of structural-thermo-atmogeochemical studies (STAGR) was used. For the first time, in accordance with the methodology, a scientific and methodological substantiation of the oil and gas prospectivity criteria (indicators) was developed at Yuliivsko-Skvortsivskyi polygon. The methodology of structural atmogeochemical research was supplemented by a new sixth block of studies in the conclusion of the dissertation. It was the realization of selected prospective areas, based on which one can select priority objects for further exploration (as detailed 3D seismic) or go directly to exploration well drilling. Based on the selected structural-tectonic criteria, it was determined that the Yuliivsko-Skvortsivskyi polygon has a complex small-block structure due to which a considerable number of tectonically-limited traps can be predicted. On the basis of the selected thermometric criterion, the spatial inhomogeneity was detected in the distribution of the temperature indices of the base layer and it was determined that the temperature survey reflects separated blocks within the Yuliivsko-Skvortsovskyi range tectonically. On the basis of the selected atmogeochemical criteria, a number of regularities were established, namely: gas-geochemical surveying of radon, toron and carbon dioxide allowed not only to confirm and clarify fault zones that are already known, but also to isolate new (most likely small-amplitude) geophymic fracture studies. Stable blocks have been installed in the geodynamic way so it is possible to predict the conservation of undisturbed tectonic processes by hydrocarbon deposits; gas-geochemical surveys of helium and hydrogen showed the confinement of fixed values in area to productive hydrocarbon deposits in the crystalline foundation; Gas-geochemical survey of hydrocarbon gases allowed to establish regularities of Yuliivsko-Skvortsivskyi polygon reflection in the fields of methane distribution and its homologs.