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

Abstract

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.

Characterization of Asphaltenes and Petroleum Using Benzenepolycarboxylic Acids (BPCAs) and Compound-Specific Stable Carbon Isotopes

“…Maltenes are NSO n -heptane-soluble substances that contain lower proportions of ConAC with a lower number of fused rings . In a petroleum matrix, asphaltene molecules are stabilized by maltenes via interactions based on steric guest-host mechanisms or intermolecular attractions, such as π-π stacking. , Thus, during asphaltene isolation, maltene impurities may remain occluded inside asphaltene aggregates. ,, If asphaltenes are not properly purified using solvent washes during the extraction process, vaporizable material may also remain occluded and affect the BPCA measurements and normalization. The occlusion of maltenes and vaporizable material will result in the underestimation of ConAC contents and B6CA:B5CA ratios.…”

“…10 In a petroleum matrix, asphaltene molecules are stabilized by maltenes via interactions based on steric guesthost mechanisms or intermolecular attractions, such as π-π stacking. 82,83 Thus, during asphaltene isolation, maltene impurities may remain occluded inside asphaltene aggregates. 52,64,65 If asphaltenes are not properly purified using solvent washes during the extraction process, vaporizable material may also remain occluded 25 and affect the BPCA measurements and normalization.…”

Is Solubility Classification a Meaningful Measure in Thermal Conversion?

“…It should further be noted that the material in this study was not washed with the same rigor as in separation protocols that required repeated washing, i.e., multistep solid–liquid equilibrium separation. The entrapment of material that is n -heptane soluble in the material that is n -heptane insoluble is possible. , Throughout the study, any reference to “ n -heptane insoluble asphaltenes” should therefore be interpreted as material separated as insoluble in n -heptane using the specific experimental protocol described in Section .…”

“…The entrapment of material that is n-heptane soluble in the material that is n-heptane insoluble is possible. 49,50 Throughout the study, any reference to "nheptane insoluble asphaltenes" should therefore be interpreted as material separated as insoluble in n-heptane using the specific experimental protocol described in Section 2.2.1.…”

Asphaltenes: Aggregates in Terms of A1 and A2 or Island and Archipielago Structures

“…The released hydrocarbons after the treatment were compared with those from the original crude oil, and used to evaluate the alteration of the oils, especially as a result of biodegradation. The authors suggest that occluded saturated hydrocarbons represent the original oil derived from kerogen, retained and protected against alteration inside asphaltenes over geological times …”