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STRUCTURE OF VEREYSKY OIL RESERVOIR FROM AKANSKOYE OILFIELD OF THE TATARSTAN REPUBLIC

E R Barieva

Abstract

The oil fields of the Vereysky horizon (C2vr) are regional oil saturated on the Tatarstan Republic and located in the oil-and-gas-bearing Serpukhovsky-Vereysky basinal complex. In the sections are interbedding of various facial types of limestone with marls, clays, and sandstones. From below upwards along the section, the proportion of the clastic component increases and the carbonate component decreases. In the anticline structure, Vireysky oil-saturated reservoirs form multilayers series. Oil reservoirs are confined to sandstones and grainstone and packstone. Wackstone, marls, and claystones form a dense type of rocks. According to petrophysical data, the porosity of oil-saturated limestone varies from 9.6 to 25.2%, permeability varies from 16.74 to 223.4 ?m2, bitumen saturation is 29.88-85.04%; the residual water content is 24.01?57.6%; equivalent pore diameter is 1.54-14.38 microns. In spite of good reservoir characteristics of reservoir rocks, some of them do not produce hydrocarbons during oil development. The study of the oil composition in the reservoir showed that they differ in the ratio of hydrocarbon fractions. In the upper parts of the Vereysky oil-saturated level, light and medium hydrocarbon fractions predominate, in the lower parts predominate heavy fractions. Multilayer reservoirs are not connected hydrodynamically with each other. This form ?puff pie? from interbedded reservoir oil-saturated rocks with different degrees of oxidation. The intensity of natural water flooding of oil reservoirs deposits is determined by reservoir properties of reservoir rocks. It depends, the larger the pore-cavern sizes in carbonate reservoirs, the higher the probability of penetration of outside waters into the oil reservoir.

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