The Distribution Model for Hydrocarbon Compounds in a Pores Space of the Bazhenov Formation

The results of studies of the molecular compositions of hydrocarbon compounds (HCCs) in open and closed pores of oil-source rocks of the Bazhenov Formation are presented. It was shown that the use of solvents of different polarities provided a method for additional HCC extraction from both open and closed pores of rock samples. The HCC compositions were regularly different in both the distribution of normal alkanes and the values of biomarker parameters that characterize the maturity and sedimentation conditions. The HCCs in open pores appeared to be more thermally transformed than those in closed pores. In both cases, the maturity could be decreased in blocked pores, especially in those sealed with resin–asphaltene alcohol–benzene-soluble compounds of various compositions in open and closed pore volumes. Pr/Ph and dia/(dia+reg)C27 were regularly higher for bitumens of open pores, whereas С29/С30 and H35S/H34S were much higher in closed pores and could be varied in blocked pores relative to the open part of an area. An improved model is proposed for the HCC distribution within a pore area. The model includes the presence of residual light HCCs in open pores along with two types of blocked pores containing HCCs blocked with resin–asphaltene compounds of various compositions in both the open and closed pore spaces.