Geology and Hydrocarbon Potential of the Astrakhan Arc Subsalt Deposits in the Caspian Petroleum Province: Results of Comprehensive Study

The article summarizes the results of the authors’ work on the comprehensive substantiation of the geological, tectonic and geofluid-dynamic conditions of hydrocarbon generation and accumulation in the subsalt floor of the Astrakhan Arch inside the Caspian oil and gas province. We analyzed a significant amount of archival geological and geophysical data and materials such as (i) an array of regional seismic profiles; (ii) gravity and magnetic exploration data of different scales; (iii) results of deep drilling. Specific seismic geological bodies that are capable of serving as oil and gas reservoirs have been identified. For the first time in creating the geological model of the Astrakhan Arch, its location within the autoclave hydrocarbon system of the subsalt floor of the Central subprovince of the Caspian oil and gas Province (within the Astrakha—Jambay oil and gas accumulation zone) has been taken into account. This allowed us to substantiate the geofluid-dynamic nature of the number of large non-structural-type oil and gas reservoirs boundaries. It is opening up new possibilities for predicting oil and gas fields, including those with low sulfur content. Several generation-accumulation mini-hotbeds have been identified on the Astrakhan Arch, and in three of them—reservoirs with increased probability of discovering oil and gas fields. The main result of the study is the refinement of the initial total geological resources of hydrocarbons of the Astrakhan Arch and adjacent areas.