Features of the Composition of Compounds Trapped in Asphaltenes of Oils and Bitumens of the Bavly Oil Field

The asphaltene aggregates are made of a well-packed and stable in benzene (toluene) solution core and a loose-packed periphery, which can respectively occlude and adsorb the other oil fractions. Previously (Liaoet al.Energy Fuels2005, 180), it was proposed that the “occluded compounds have been well-protected from the secondary alteration processes that occurred in the oil reservoir and could be considered to be the original oil, whereas the adsorbed compounds have been affected by the secondary evolving processes”. In this paper, the compounds adsorbed and occluded in asphaltenes both of crude oils of the multipay Bavly oil field (Russia) and bitumens extracted from the source bed (Domanic formation) of the same oil field are studied and compared. It is found that the content of adsorbed compounds can reach up to 20% and higher and is dominated by resin components (mostly the polar resins). A comparative analysis of the structural-group and hydrocarbon compositions of oils, bitumens, and compounds adsorbed on the asphaltenes is carried out. It is found that the compounds adsorbed on oil asphaltenes are enriched with fragments of ethers, esters, and amides of acids and the high-molecular-weight n-alkanes in comparison with oil maltenes, while the composition of compounds adsorbed on bitumen asphaltenes is similar to that of bitumen maltenes. In the compounds occluded in oil asphaltenes, the homological series of normal and monomethyl substituted alkanes, which are considered to be relict hydrocarbons, are detected, while in compounds occluded in bitumen asphaltenes, the trace of high-molecular-weight n-alkanes and monomethyl substituted alkanes only. The obtained data indicate that compounds adsorbed on asphaltenes, like occluded compounds, can also characterize the composition of the original oil (protopetroleum) and that there may be a correlation between the oil and the bitumen of the Bavly oil field.