Geochemical Characteristics of Bitumen "A" in Marine Carbonate Rock from the Tarim Basin

The marine carbonate rocks were crushed in to powder before taking chloroform solvent extraction by the Soxhlet apparatus. The soluble organic components were separated by column chromatography to yield saturated hydrocarbon, aromatic hydrocarbon and non-hydrocarbon after the asphaltene was precipitated by hexane. The saturated hydrocarbon and aromatic hydrocarbon were directly measured by Gas Chromatography-Mass Spectrometry (GC-MS). The non-hydrocarbon was esterified by BCl₃-CH₃OH mixed solution before taking measurement by GC-MS. The analysis result showed that the organic matters have undergone a high degree of evolution and the kerogen type is dominated by the aquatic organisms. The platform facies hydrocarbon-generating paleoenvironment was sulphur microorganism enriched saline deep water reducing environment. The organic matters of samples have experienced the strong process of cyclization-aromatization and demethylation, which were helpful to the generation of natural gas mainly with methane. The detectable long mid-chain ketones (C₃₁-16-one, C₃₃-16-one and C₃₅-18-one) in the aromatic hydrocarbon might be the particular biomarkers about the presence of the organic acid salts.