Due to the increase of the volume of hard-to-recover oil reserves in the fields with a complex structure of reservoir rocks, a high degree of their heterogeneity and low filtration capacitive properties, the authors studied lithological and facies researches and correlation analysis of the reservoir properties of the Bashkir sediments of the Gagarin field as a bright representative of the described type of fields. The rates of open porosity and absolute permeability on gas were studied and analyzed, and facies in the rocks of this deposit were characterized. As a result of the description, coastal marine shallow-water facies and marine shallow-water facies of the open sea were identified. Among the last, the facies of shoals and some facies of settlements of various organisms were identified, including algae settlements, foraminifer settlements, and facies relatively flat seabed with a mobile and calm hydrodynamic regime. The data, including the rates of porosity, permeability and residual water saturation, was analyzed separately for each facies. The correlation dependences of the permeability coefficient on porosity and residual water saturation on porosity were constructed for the established facies, and the nature of their relationship was identified and regression equations were derived. The research revealed a strong and significant relationship of the studied parameters for both selected facies of the settlements of different organisms, as well as for the facies of the areas of the flat seabed with a calm hydrodynamic regime, weak and insignificant - for the facies of the areas of the flat seabed with a mobile hydrodynamic regime. The absence of correlation between the parameters was found for the sediments of shoal facies and coastal marine shallow-water closed ones, and for the last the correlation of porosity and residual water saturation was not established due to the lack of data.
Based on the research several conclusions were made. The development of pore and cavernous reservoirs is controlled by the predominant types of rocks – algae limestones. In the Bashkir sediments, among others, the predominant importance belongs to the facies of settlements of various organisms. The correlation analysis for the Bashkir sediments revealed the strongest and most significant relationship of porosity and permeability for the facies of the areas of the flat seabed with a calm hydrodynamic regime, algae settlements and foraminifera settlements, and the relationship between porosity and residual water saturation for the facies of the algae settlements and the areas of the flat seabed with a calm hydrodynamic regime.
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