The paper provides results of the field-geological information analysis in order to evaluate the current development stage of reservoir Yu1 of the Verkh-Tarskoe oilfield. The main recoverableasset is currently indevelopment phase III (declining production). The total well stock consists of 175 wells, of which 134 are producing.The monthly volume of water injection into the reservoir pressure maintenance (RPM) system reaches 100,000 m3, and fluidproductionis about 170,000 m3 with averagewater flooding of producing wells is90.4%. The structures with complex geometry thatformedwithin thehydrodynamic field where the deep pressure sinks are associated withproduction wells, and piezomaximawith injection wells.Given the multi-facies pattern of thesandstone depositional environmentsand secondary processes ofrocks metamorphismduringcatagenesis, thetarget reservoirhas a complex structure and its study in greater detail willrequirebuilding a new geological modelof the oilfieldand more precisedefinition engineeringto achieve maximumrecovery.