Dynamics of naphthidogenesis in the Devonian deposits of the Dobrudja Foredeep
Authors:   Institute of Geology and Geochemistry of Combustible Minerals of the National Academy of Science of Ukraine, Hnidets Volodymyr , Hryhorchuk Kostyantyn ,   Institute of Geology and Geochemistry of Combustible Minerals of the National Academy of Science of Ukraine, Koshil Lesia ,   Institute of Geology and Geochemistry of Combustible Minerals of the National Academy of Science of Ukraine, Yakovenko Myroslava ,   Institute of Geology and Geochemistry of Combustible Minerals of the National Academy of Science of Ukraine
Published: December 2024

The aim of the work was to find out the dynamics of naphthidogenesis in the Devonian deposits of the Dobrudja Foredeep. The studies were conducted using retrospective analysis based on the fluid-dynamic concept of catagenesis. As a result, a difference in the catagenesis regime in different parts of the depression was established for the first time. The generation and accumulation of hydrocarbons in the Tuzliv Depression and the Furmanivsk-Prymorsk region exhibit distinct characteristics. The primary phase of oil formation in the Tuzliv Depression is associated with the first cycle of accumulation. In contrast, gas formation in the Furmanivsk-Prymorsk region is linked to the second cycle of catagenesis. Features of spatial and age heterogeneity of hydrocarbon accumulation were predicted. During the first cycle of catagenesis, the most intense flows of petroleum fluids were directed toward the centricline of the Tuzliv Depression, which consists of Middle Devonian deposits. This flow pattern likely played a significant role in the formation of the East Sarata deposit. Additionally, it supports a positive assessment of the prospects for the surrounding areas, including the Saratska, Yaroslavska, Rozivska, Hryhorivska, and Saryyarska structures. At the same time, early-generation gas was formed in the Furmanivsk-Prymorsk Depression. During the second cycle of catagenesis, it is predicted that oil deposits will form in the Lower Devonian sediments on the northern side and in the Upper Devonian sediments on the southern side. Additionally, gas deposits are expected to occur in the Silurian and ancient layers along the western centricline. In the final cycle of catagenesis within the Tuzliv Depression, the processes leading to oil accumulation in the Middle Devonian deposits at the periphery of the depression and gas accumulation in the Lower Devonian formations along the centricline decreased. Conversely, the accumulation of gas hydrocarbons in the Lower Devonian and underlying formations became more pronounced in the Furmanivsk-Prymorsk Depression. The hydrocarbon deposits predicted in the Lower Devonian sediments and older formations may act as intermediate reservoirs. This would allow hydrocarbons from deeper layers to migrate upward into overlying formations via the extensively developed disjunctive faults in the region. The scientific novelty lies in the establishment of lateral heterogeneity of the catagenesis regime and the corresponding heterogeneity of oil and gas formation processes. The practical significance lies in the identified specificity of the development of oil and gas accumulation zones and the localization of promising areas.