Types of reservoirs of the Ufa stage of the Republic of Tatarstan. Genesis and reservoir properties

Abstract

In this paper, we studied core material from well No. 15 of the extra-viscous oil field, geographically located within the western border of the South Tatar arch. Under laboratory conditions, reservoir properties (porosity, permeability), oil saturation and particle size distribution of Sheshmin sandstones were measured. It was established that the terrigenous reservoir belongs to class I and II according to the classification of A.A. Hanin, with high permeability. In addition, in well No. 15 , a downward trend was identified in reservoir properties downstream of the section, the reason for which is probably the migration of underlying formation waters from carbonate sediments of Sakmar age. By analyzing the grain size data distribution, the reservoir is represented by well-sorted fine-grained sandstone with a dominant fraction of 0.1-0.25 mm (about 65% of the entire sample); paleodynamic analysis was carried out using the Passega diagram; It was established that the formation of the reservoir took place under conditions of gradation suspension (P-Q-R area in the diagram), in the lower parts of fast river flows, directly at the bottom. The findings are consistent with data from previous researchers. According to the study of the cores of other wells, maps of changes in reservoir properties have also been constructed, which highlighted reservoir zones with high reservoir properties – the central parts of the North and South Uplifts.