Methodology for applying the volumetric method for estimating the hydrocarbon resources based on pyrolysis data in the Bazhenov formation are considered in the article. The analysis of the powder and the pieces of rock pyrolysis results before and after extraction are presented. Based on the study of more than 8000 samples, a new scheme for processing pyrolysis results of the powder before and after extraction with chloroform is proposed. It is emphasized that it is necessary to estimate the loss of light oil from the core due to its extraction to the surface by measuring the gas porosity. Since in the reservoir conditions neither effective heating of rocks nor its breaking to a powdery state is possible, pyrolysis of pieces of rock is being investigated in the work. The shift of the quantitative yield of hydrocarbons from peak S1 to peak S2 as the size of the samples increases is especially interesting. These studies illustrate in detail the effect of the degree of fragmentation on the results of pyrolysis and make it possible to estimate how much the extraction of hydrocarbons in the reservoir will be worse than in the laboratory. The ratios of the absorbed hydrocarbon compounds and the products of the kerogen cracking in the organic matter of the Bazhenov formation depending on the degree of its catagenetic maturity was also studied. It is recommended that assessments be carried out taking into account the degree of maturity of the organic matter, excluding from consideration areas of unconverted kerogen. The calculation of geological reserves and hydrocarbon resources in reservoirs that are close in properties conventional ones is recommended to be performed by a volumetric method. It is advisable to calculate the recoverable oil reserves using different versions of the statistical method taking into account production decline rate.
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