Routine GC/MS analysis may apply to the volatilized Low-Molecular-Weight compounds in saturate and aromatic hydrocarbon fractions;thus,relative studies using this technique inevitably bring about some limitations on distribution of miscellaneous sulfur atom.In this article,Fourier Transform Ion Cyclotron Resonance Mass Spectrometry(FT-ICR MS)with high resolution is employed to investigate the distribution of organic sulfur compounds(OSCs)in the crude oil typically derived from the Eogene carbonate-evaporite sediments with further chemical compositional characterization in molecular level by miscellaneous atomic type,carbon number,and double bond equivalent(DBE).A variety of miscellaneous atomic types with S1,S2,S3,OS,OS2,O2S,O2S2,NS,and NOS etc.(S1 means those OSCs with one sulfur atom in a molecule)were identified in OSCs in these oil samples.High levels of alkyl thioether series compounds with one ring structure were presented mainly in the crude oil in the Jianghan Basin whereas high amounts of benzothiophene,dibenzothiophene etc.compounds with higher values in DBE and carbon number range occurred in the sulfur-rich heavy oil in the Jinxian Sag.Although carbonate-evaporite sediments deposited in the saline lacustrine facies in the Eogene basin both occurred in the Jinxian Sag and Jianghan Basin,obviously,they possess different chemical diagenetic pathway of sulfur under various microbial reactions,leading to diverse distributional characteristics on biomarkers,OSCs,and even different hydrocarbon generation mechanism of immature crude oil.
LU HongSHI QuanMA QingLinSHI YangLIU JinZhongSHENG GuoYingPENG PingAn
High abundant sulfur-containing steroids were identified and detected in saturate hydrocarbon fractions of heavy oil with a high sulfur content in the Jinxian Sag,Bohai Bay Basin,North China.These sulfur-containing steroids were structurally merged into the D-ring of steroid nucleus with thiophene ring and/or combined into the C-22 in the side-chain.Based on the previous reports of sulfur-containing steroids with methylthio-steroids and intra-molecular form,four formation mechanisms of sulfur-containing steroids and diagenetic pathway of steroids under S-rich conditions were proposed in this paper according to the double bond positions in the sterene compounds.Hydrogenation and sulfurization both occurred in the diagenetic processes of olefinic bond in the side-chain of steroids:abiogenic chemical hydrogenation of H2S and HS-leads to the formation of regular steranes;a successful sulfurization process leads to the formation of the side-chain sulfur-containing steroids whereas unsuccessful cyclization and/or sulfurization result in the generation of short-chain steranes.This kind of mechanism of hydrogenation/sulfurization of side-chain olefinic bond provides a potential genesis clue for the occurrence of high abundance of short-chain steranes(higher than the common regular steroids,phytane and n-alkanes)in S-rich heavy oils and source rocks in the Jinxian Sag,Bohai Bay Basin,North China.
LU HongWANG QingTaoJIANG LinXiangZHANG HuiLIU JinZhongSHENG GuoYingPENG PingAn
