Hydrogeological aspects of the hydrocarbon deposit formation within the northern framing of the Caspian Lowland

Abstract

The formation of oil and gas deposits in the near-port zones of the Caspian Basin is associated with the generation of hydrocarbons in deep-submerged zones and its subsequent migration to the near-port zones. The migration of oil and gas occurs together with reservoir waters. Under these conditions, the identified gas-hydrochemical anomalies in the instrument zones of the depression are important in determining the routes of hydrocarbon migration and oil and gas accumulation zones. The article analyzes the hydrogeological situation in the subsalt Paleozoic sediments in the junction zone of the Volga-Ural anteclise and the Caspian basin, describes the salt composition of reservoir waters, and the composition of water-dissolved gases. The waters of anomalous composition are identified, which indicate the predominant migration of reservoir waters towards the Volga-Ural anteclise. In the Devonian sediments of the region, anomalies are distinguished by the appearance of reservoir waters of a reduced degree of metamorphization, or their reduced mineralization (desalinated water). The identified anomalies allow us to identify zones favorable for the migration of reservoir waters and hydrocarbons, zones of oil and gas accumulation. These studies can be used to interpret the results of geological exploration for oil and gas in the port zones of the Caspian Basin.