The integration of lithologic and physical and special investigations of the core is carried out in order to study the possible reasons for reservoir capacity reduction. The object of the study was sandy-silty rocks of producing YuV1 reservoir of Uryevskoye field, characterized by heterogeneous composition of the argillaceous cement and its nonuniform distribution (microinhomogeneity). Kaolinite, chlorite, hydromica minerals are allocated as part of the cement composition. Lithological-technological typification of reservoir rocks with contouring areas of their distribution is carried out with account of clay minerals amount in the composition of rocks and their different ability to swell. Total four basic types are allocated: I - the high content of hydromicaceous minerals; II, III - respectively intermediate and high content of kaolinite; IV - the absence of argillaceous cement. Rocks type I distribution area is the most susceptible to swelling. In such circumstances it is necessary to use highly mineralized water in the reservoir pressure maintenance system. Rocks type III distribution areas are less prone to swelling, so water with lower salinity can be injected for the reservoir pressure maintenance system. There are no injected water mineralization constraints in rocks type IV distribution areas. The results of experiments on models, consisting of a core sample types II and III, show that rock permeability slowly reduces since the beginning of the injection. The most significant reduction of permeability is fixed for rocks type II. This presumably is due to kaolinite content decreasing and increasing the proportion of chlorite and hydromica minerals in the argillaceous cement compared to type III.
It is suggested that one of the possible reasons for reducing the permeability of the YuV1 reservoir is microinhomogeneity of rocks of allocated lithological-technological types and their non-uniform distribution over the area.
