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
(
Liao
Liao
Energy Fuels2005180), 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.
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