BLACK SHALES OF SILURIAN AND DEVONIAN DEPOSITS OF THE FORE-DOBROGEA TROUGH

Abstract

The article discusses the structural features of the Paleozoic (Silurian and Devonian) deposits of the Fore-Dobrogea Trough, a promising oil and gas region of Ukraine, with the aim of identifying black shale strata enriched with organic matter in them. Such strata under certain geological-thermobaric conditions obtain oil and gas generating properties and can be sources of hydrocarbons. This study included analysis of the core data and geophysical logs of deep wells and the cyclostratigraphic division of the Silurian and Devonian deposits. Within the sedimentation cycles of the Silurian and Devonian, the stratigraphic levels of the black-shales strata have been identified. Features of their lithological composition, the facies-geochemical conditions of accumulation, and spatial distribution have been determined. Carbonate-terrigenous strata of the Skal horizon of the Lower Silurian and clay strata of the Upper Silurian developed in the depressions of the Fore-Dobrogea Trough and island Zmiinyi, are classified as strata of the black shale type. They are characterized by a high content of sapropel organic matter. In the Middle-Upper Devonian sedimentary complex, the most significant black-shale strata is the Middle Devonian (Givetian), composed of alternating marls and pyritized argillites, accumulated in the reducing conditions of the aquagenic basin, which was favorable for the formation of petroleum bitumoids. Based on these studies, the prospects for the oil and gas content of the Fore-Dobrogea Trough have been substantiated.