Geology, geography and global energy

Scientific and Technical Journal

Paleozoic reefs of a south-western part of Caspian basin

2017. №2, pp. 30-38

Fedorova N.F. - C.Sc. in Geology and Mineralogy, Associate Professor, Astrakhan State University, 1 Shaumyan sq., Astrakhan, 414000, Russian Federation,

Bystrova I.V. - C.Sc. in Geology and Mineralogy, Associate Professor, Astrakhan State University, 1 Shaumyan sq., Astrakhan, 414000, Russian Federation,

Zavyalov A.V. - master, Astrakhan State University, 1 Shaumyan sq., Astrakhan, 414000, Russian Federation,

The subject of research is the subsalt deposits of the sedimentary cover of the southwestern part of the Caspian basin. Experience in oil and gas exploration abroad and in our country shows that a significant portion of the world's known oil and gas reserves are confined to the traps of non-structural type, the buried reef structures of various morphogenetic types. There is a wide variety of productive reef structures, different features of the geological structure and regularities of distribution. Such deposits are characterized by stocks, up to several hundred million tons. Square deposits vary widely. The specificity of the structure of each type determines the methods of their identification and exploration works. A favorable factor for the occurrence of reefs is the rapid subsidence of the sea bottom of the pool. The Caspian basin is an area of long uncompensated sediments subsidence. As a result of this process in subsalt sediments were buried, a giant amount of sedimentary rocks predominantly of marine origin. The impact and tectonic activity, which contributed to the creation of dissected bottom topography, and thereby provided entry to the reef's clear waters with a high content of nutrients. Reef rocks have high reservoir properties. For them characteristic of primary and secondary porosity, and fracturing. The aim of this work is to allocate on the basis of geological and geophysical data of prospective oil and gas areas associated with reef formations in the subsalt part of the section within the South-Western part of the Caspian basin. High oil and gas potential of the Paleozoic reefs are associated with the South-Western part of the caspian basin - the territories of the Astrakhan arch. The materials of exploration of the last decades on the territory of the Astrakhan arch allowed us to obtain convincing evidence that the chronicle is a standalone in-basin carbonate platform, Devonian Bashkirian age. For widespread, significant amplitude of reef structures and favorable conditions of accumulation and preservation of hydrocarbons in them, this area is a unique region. Searching for deposits in a stratigraphic range from Carboniferous to Devonian sediments are considered as the most effective and promising direction of exploration of the Russian oil and gas companies at the present time.

Key words: Прикаспийская впадина, Астраханский свод, Caspian basin, Astrakhan arch, subsalt sediments, reefs, carbonate platform, petroleum systems, hydrocarbon deposits, deposit porosity, trecinvest, подсолевые отложения, рифы, карбонатная платформа, нефтегазоносны