Chemical structure and biomarker content of Jinghan asphaltenes and kerogens

The compound classes and biomarker compositions of immature Jinghan crude o il asphaltenes and their potential respective source rock kerogens have bee n investigated by chemolysis. The C-S-, C-O-, and C-arom-C-bound appendages have been liberated by Ni2B reduction, BBr3 hydrolysis, and ruthenium-ions -catalyzed oxidation. Measured were the saturate, aromatic, and polar (+ as phaltene) compound classes and the homologous series of hydrocarbon biomark ers: n-alkanes, regular isoprenoids, steranes, 4-methylsteranes, hopanes, g ammacerane, their monocarboxylic acid derivatives, and alpha-omega-di-n-alk anoic acids. The nature and distribution of the biomarkers in shallower dep ths reveals a good correlation between the crude oil asphaltene and the ker ogen, manifesting a crude oil-source rock relationship. In deeper strata, t he correlation is less convincing but there is no indication of incompatibi lity. The biomarker composition confirms the immaturity of this deposit, an d the huge (53%) yields of C-S plus C-O bond cleavage products from the hig h-sulfur asphaltene set this type of asphaltene aside from mature crude oil asphaltenes. Also, the biomarker composition. points to a strongly reducin g, lacustrine depositional environment for this deposit.