Structure and composition of the Sarailinsky depression oil source strata in territory of the Tatarstan Republic

The work carried out a study of core material from oil source rocks of the Sarailinsky depression, located between the southern and northern domes of the Tatar arch within the Tatarstan Republic. The well sections of the Sarailinsky strata are dominated by carbonate rocks, represented by packstones, wackestones and mudstones. Among the limestones lie interlayers of carbonate-siliceous rocks and mudstones. All rock lithotypes are enriched to varying degrees in sapropelic organic matter, which allows them to be classified as oil source deposits. There is a tendency for the relative content of organic matter to increase in the series: limestone → carbonate-siliceous rocks → mudstones. Judging by the interlayering of rocks of different composition in the section, the formation of the Sarailinsky strata took place in a marine sedimentation basin, with periodically changing environmental conditions. Under normal conditions, limestone was formed, under abnormal conditions, carbonate-siliceous rocks enriched in organic matter were formed, and when the removal of terrigenous material from the continent intensified, argillites were formed.