Methodological Approaches to the Calculation of Reserves of the Bazhenov Formation

The authors propose an algorithm using the volumetric method for reserves calculation of the Bazhenov Fm in one of the fields within the West Siberian Petroleum Province. It is suggested to consider two reservoir types. 1st type reservoir is a porous reservoir with net thickness determined in accordance with the direct qualitative features on the basis of log and core data. 2nd type reservoir is identified on the basis of PL data in the producing intervals after fracturing or some other stimulation/treatment. Before fracturing, total reservoir thickness over the well is determined basing on the statistically revealed relationship between thickness of 1st and 2nd type reservoirs. Porosity and oil saturation are determined from core and log data. The proposed algorithm allows to identify as reservoirs the permeable intervals characterized by the direct qualitative indicators or inflows in accordance with PLT, instead of lithotypes or beds with certain geochemical features. The authors believe that analysis of all the material complied on the problem allows making a conclusion that today there is still no rigorous solution for reserves assessment in the Bazhenov-type formation.