Chepil V. Geological conditions of formation and explorationt of unconventional hydrocarbon sources of Volyn-Podillya.

The thesis is devoted to the study of the prospects of industrial oil and gas bearing non-traditional sources of hydrocarbons of Volyn-Podillya. The most important results of the research carried out in the theoretical and scientific-practical aspects are the establishment of clear representations about the nature of non-traditional hydrocarbon sources, the peculiarities of generation, migration and accumulation in the sedimentary strata of Volyn-Podillya, where previously no such purposeful work was carried out. The peculiarities of the geological structure of the Silurian and Cambrian strata of the study area, the conditions of their formation, geological, geochemical, and other quantitative factors for predicting the prospects of industrial gas bearing of Silurian shales and Cambrian compacted sandstones were studied. The favorable geological and industrial preconditions for the formation of hydrocarbons of Silurian shales and Cambrian compacted sandstone deposits were scientifically substantiated. The established quantitative factors for the prediction of hydrocarbons and their comparison with the well-known deposits of North America testify to the high prospects of gas bearing of the black-shale Paleozoic strata of Volyn-Podillya. Among these, the greatest prospects are associated with the black-shale deposits of the Upper Silurian. They are a top priority for further exploration where gas was generated at high levels. This made it possible for the first time to definitely consider the black-shale thickness of Silurian as the entire potential gas deposit. The development zone covers an area of 320 km from northwest to southeast with an area of about 16 thousand km2. It is confirmed by more than 30 wells and belongs to the central part of the Lviv Paleozoic deflection and the north-eastern part of the Precarpathian deflection. Estimation of the prognosis gas resources of the black-shale deposits of Volyn-Podillya was performed according to the methodology of the US Geological Survey for the poorly explored territories and amounts about 12 trillions m3 and the recoverable resources about 1.8 trillions m3. According to the quantitative values of the main factors of the gas-bearing prediction Rava-Rusko-Krekhivsk and East-Lischinsk were selected as the high-priority gas areas in the Silurian shale strata within the Lviv-Kolomyya structural and facial zone with recoverable resources about 146 billions m3 and 98 billions m3. For the сontouring of prospective shale formations, a special complex of regional deep seismic surveying 2D with the methods of electric exploration, caused by polarization on profiles of a network of seismic profiles with a length of 1.5 thousand running kilometers, gravimagnetic and geochemical surveys, are proposed. Based on the determined quantitative values of the factors of prediction of gas accumulations in compacted sandstones it is proved that the most promising stratigraphic complex for gas search in Volyn-Podillya is Cambrian deposits. The prospects of their industrial gas-bearing capacity are related to the zone of development of rocks with unsatisfactory filtration-capacity properties over an area of more than 6000 km2. The prognosis recoverable gas resources of the area are estimated around 340 billions m3. There is a selected high-preority zone of 1250 km2 within the perspective area of the gas-bearing compacted Cambrian sandstones. Its prognosis recoverable gas resources is approximately 200 billions m3, and its high prospects are also confirmed by the intense gas seeps during drilling wells of Cambrian sealed collectors. Non-traditional sources are difficult to extract and they are high-cost. However the significant resources of hydrocarbons and the rapidly evolving technologies make them quite attractive and cost-effective. So far as all these unconventional sources are characterized by similar mining and geological conditions of the occurrence and require modern and practically identical technologies of discovery and extraction then the benefits of prioritizing their development are first and foremost related to the quantity of the prognosis recoverable resources. On this basis, black shale deposits of the Silurian are more priority for development. The results of the dissertation research and implementation of the practical recommendations will contribute to the effective solution of the problem of complex development of all types of hydrocarbon sources of Volyn-Podillya, which will be a significant contribution in increasing the production of hydrocarbon raw materials in Ukraine. Keywords: Volyn-Podillya, black shale deposits, compacted sandstones, shale gas, gas resources.