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The structure of geological sections of the Visean stage of small oil fields in the Western Zakamya region of the Tatarstan Republic is considered. It has been established that potentially oil-bearing deposits are carbonate-terrigenous deposits of the Tulian-Bobrikian horizon and carbonate deposits of the Aleksininian horizon. In the Tulian-Bobrikian sediments, oil deposits are localized in fine-grained quartz sandstones, the cap rocks are dense claystones. Due to the small thickness of the layers of oil-saturated sandstones, their development is not very promising. In the deposits of the Aleksininian horizon, oil deposits are localized in cavernous limestones overlain by dense diagenetic dolomites. The thickness of the oil reservoirs is 2.0-2.5 m, which allows them to be considered as potential targets for development. The presence of sulfate mineralization in the pores of reservoir rocks suggests that the oil deposits of the Aleksininian horizon are at the initial stages of waterflooding..

The sections of the coal-bearing strata of the Visean stage of the Kama coal basin in the territory of the Tatarstan republic are considered. It has been established that a coastal-marine terrigenous complex represents the coal-bearing strata. The complex is characterized by alternation of layers of coals, claystones, siltstones and sandstones. Coals lie at the base of the section, forming seams up to 10.0 m thick. Coals are allochthonous, formed due to the denudation erosion of peat deposits on land, the transfer of peat by water flows, and their sediment on the coastal part of the sea basin with normal salinity. The Visean caustobioliths can be classified as brown coals with a low degree of metamorphism. Their composition is dominated by the fusen component with scattered inclusions of liptinite and fusinite. In terms of material and petrographic composition, caustobioliths are classified as fusen varieties of gumite coals. In terms of the content of mineral impurities, the coals are low-medium ash, sulphurous.

Continental carbonate formation in low-mineralized flowing waters of temperate latitude is rare phenomenon. Taking this into account a study was conducted of crustate and stalactite-like authigenic calcite aggregates formed in the thalwegs of the ravines of the Volga Upland. According to chemical and isotopic analysis, modern carbonates are formed from poorly mineralized, meteoric waters of medium hardness, hydrocarbonate-magnesium-calcium hydrochemical type. It has been established that newly formed carbonate aggregates are characterized by the predominance of lightweight carbon and oxygen in the crystal structure. The osmotic hypothesis of the formation of lime-calcite aggregates is proposed.

The development of the Lower-Karmalinsky bituminous deposit is currently made by the SAGD method. However, focusing on the reduction of bitumen viscosity, the problem of mineral phase’s transformation at the reservoir due to anthropogenic impact overlooked. In this work, using thermodynamic modeling, shown that the injection of superheated steam into bitumen-saturated sandstone layer will lead to the dissolution of calcite cement.