Geochemical Explication of Sulfur Organics Characterized by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry on Sulfur-Rich Heavy Oils in Jinxian Sag, Bohai Bay Basin, Northern China

Abstract

For the sulfur-rich heavy oils in Jinxian Sag, Bohai Bay Basin, northern China, high abundances of organic sulfur compounds (OSCs), including benzothiophenes and dibenzothiophenes, were detected in aromatic hydrocarbon fractions. Short-chain (such as 20-thienylpregnanes and thienylandrostanes) and regular carbon-numbered S-containing steroids are also present in the saturate hydrocarbon fractions. In addition, a series of short-chain steranes (C21–26), unusual short-chain lanostanes (C24–25), 4-methyl steranes (C22–23), 4,4-dimethyl steranes (C22–24), and androstanes (C19–20) were found, accompanied with high-molecular-weight analogues, C27–30 regular steranes, C27–30 4-methyl steranes, and C28–30 4,4-dimethyl steranes. The distinctive distribution characteristics and dominance of the short-chain steroids in these oils are believed to be derived from the cleavage of the weak C–S bond at C-17 and C-20 positions of extensively sulfurized steroids with subsequent microbial attack or bacterial reworking. To o...