Comparison between immature and mature aromatic homologous series constituents in rock extracts from Well Han-2
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Comparison has been made of the occurrences of aromatic series in the chloroform fractions between immaturr and mature sedimentary rocks from Well Han-2 in the Qaidam Basin. According to the general formula CnH2n−p (p=6,8,10, …, 20), the molecular ion distributions of 11 series have been studies by capillary gas chromatography and GC-MS. It is found that the evolution of aromatic homologues from immature to mature obeys the thermodynamic rule and can be summarized as: (1) The alkyl side chains decrease and become shorter in the compounds of each series; (2) Alkyl and cycloalkane aromatics (1−3 rings) increase, but cycloalkane aromatics with more (4–5) rings decrease; (3) Aromatization is observed in alkyl benzene, alkyl naphthalene and alkyl phenanthrene series; and (4) The bimodal distribution of carbon number curves changes into unimodal distribution.
It seems that the variation in aromatic homologue distribution can be used as an effective indicator of maturation or as fingerprints for oil/source-rock correlation.
KeywordsCarbon Number Alkyl Benzene Qaidam Basin Cycloalkane Alkyl Side Chain
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