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

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• 作者：Hong Lu ; Pingan Peng ; Chang Samuel Hsu
• 刊名：Energy & Fuels
• 出版年：2013
• 出版时间：October 17, 2013
• 年：2013
• 卷：27
• 期：10
• 页码：5861-5866
• 全文大小：362K
• 年卷期：v.27,no.10(October 17, 2013)
• ISSN：1520-5029

文摘

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 (C_21鈥?6), unusual short-chain lanostanes (C_24鈥?5), 4-methyl steranes (C_22鈥?3), 4,4-dimethyl steranes (C_22鈥?4), and androstanes (C_19鈥?0) were found, accompanied with high-molecular-weight analogues, C_27鈥?0 regular steranes, C_27鈥?0 4-methyl steranes, and C_28鈥?0 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鈥揝 bond at C-17 and C-20 positions of extensively sulfurized steroids with subsequent microbial attack or bacterial reworking. To overcome the limitations of routine gas chromatography mass spectrometric analysis, which are only suitable for analyzing volatile and nonpolar saturate and aromatic hydrocarbon fractions, and to obtain more information and overall cognition on macromolecular OSCs in highly complicated petroleum substrates, such as polar NSO and asphaltene fractions, electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry was employed for the analysis of Jinxian heavy oils after methylation pretreatment. The results revealed that very complicated sulfur (S₁, S₂, and S₃) and oxidized sulfur (OS and OS₂) compounds were present in the Jinxian heavy oils, with the absence of nitrogen-containing compounds. In addition, the distribution of the most abundant S₁-type OSCs was featured by a series of compounds with a wide range of double bond equivalent (DBE) values of 1鈥?4 and carbon numbers of 10鈥?4. On the basis of the reported carbon number distributions of steroid biomarkers in these oils, the most abundant OSCs in Jinxian oils with DBE = 5鈥? in the vicinity of C_19鈥?2 and C_28鈥?0 might come from the short-chain and regular S-containing steroids. The occurrence of abundant S-containing steroids was the results of extensive sulfurization during early diagenetic stages because much more double bonds, hydroxyl groups, and carbonyl groups exist in sterols and sterenes, which are prone to attack by inorganic sulfur.