Гетерогенність літогенезу відкладів силуру Волино-Поділля

Abstract

The paper examines the features of the lithological-lithmological structure and the regime of catagenesis of the Silurian sediments of the Lishchynska and Rava-Ruska sections of Volyno-Podillya. It is shown that in the direction from the southwest to the northeast, the role of carbonate rocks in the composition of the stratum increases, which is connected with the established facies zonation. However, the structure of the section in these areas is different: in Rava-Ruska, it is more thinly layered. The sediments are also characterized by the spatial and age heterogeneity of the distribution of carbonate lithmites: in the first case, they tend to the boundary of the Upper and Lower and the middle of the Upper Silurian, and in the second case, they are developed in the tops of the Lower, in the lower, middle, and upper parts of the Upper Silurian. Attention is drawn to the significant role of clay and the absence of marl formations in the deposits of the Rava-Ruska-1 well, which testifies to the heterogeneity of sedimentation conditions in the mesopelagial of the Silurian basin. The cyclic nature of Silurian sedimentation is established. At the same time, four regressive episodes are recorded in the Lishchynska area, and five in Rava-Ruska, which may indicate a certain specificity of sedimentation conditions in different parts of the basin. The latter directly affects the peculiarity of the spatial-age distribution of reservoir rocks and aquifers. It is shown that the post-sedimentation transformations are mainly related to the development of authigenic silica and calcite, which is found in both clayey and carbonate rocks. A significant difference in the history of the formation of the oil and gas systems of the Lishchynska and Rava-Ruska areas has been established, which allows us to assess their prospects differently. Thus, in the first case, the generation potential of organic matter of Silurian sediments was largely exhausted by the end of the Mesozoic. In the second, large-scale processes of generation and migration of hydrocarbon fluids began only in Paleogene-Neogene time.