Interruptions in sedimentation as a factor in the growth of heterogeneity in pre-salt deposits (on the example of the Caspian and Volga-Ural oil and gas provinces)

Abstract

The study of breaks in sedimentation is of interest in various aspects. The role of biogenic and chemical sulfate reduction in the dissolution of carbonate rocks is emphasized. The formation of reservoirs of different genesis in sediments was established in the tested cases of erosive action. As a result of deep processing of deposits, identified denudations and the formation of a weathering crust, the conditions for the formation of large reservoirs of hydrocarbons in its thickness. The role of breaks in the change in the sedimentation regime in the marine on the continental part is considered; appearance of humic organic matter (OM) in sedimentary deposits of the Late Paleozoic. Representatives of representatives of humic OM in pre-salt deposits of the Caspian oil and gas province are given. In the Volga-Ural region, coal-bearing deposits of erosion-karst paleoincisions enhance the heterogeneity of Carboniferous deposits at catagenic depths. A feature of the relief of the erosion-sedimentary surface formed within the Astrakhan carbonate massif is noted. Fragments of alluvial fans preserved from erosion are fixed here. An analysis was made of the relationship between breaks in sedimentation and catagenetic unconformities. Keywords: Interruption; Carbonate deposits; Karst; Catagenesis; Collector; Oil and gas bearing; Reservoir.