摘要:
摘 要 [目的]富粘球形藻(Gloeocapsomorpha Prisca, G. prisca)的奥陶系Kukersite型油页岩在全球古生界范围内是一套重要的烃源岩，但是中国仅在塔里木盆地获得零星的检出和报道，因此，快速鉴定G. prisca于烃源岩中是否存在于烃源岩中是一项重要的地球化学工作。干酪根是生烃母质的富集产物，因此可通过干酪根对烃源岩进行快速追踪。[方法]为此，对爱沙尼亚油页岩样品的干酪根进行了快速连续分步热解实验，在360~610 ℃范围内以50 ℃为间隔开展分步热解。[结果与讨论]结果表明，热裂解产物均以5-正烷基-1,3-苯二酚及其同系物为主，并以高含量的短链烷烃为特征，但在560 ℃出现部分异常的高碳数（＞nC29）正构烷烃；在中高温度点（460~560 ℃）持续出现烷基苯、烷基噻吩和烷基酮系列化合物。热解产物均具有展现出低碳数和富烷基链的特征，并在460~510 ℃呈现一定的奇碳优势。热解产物中极其丰富、持续产出的5-正烷基-1,3-苯二酚类同系物，不仅能够帮助快速确认烃源岩是否富G. prisca，而且不同温度点的热解产物组成特征、变化和对比有助于干酪根结构研究。快速分步热解产物变化表明，在G. prisca中存在以5-正烷基-1,3-苯二酚为主的聚合形成的生物大分子结构。聚合物大分子中的不同单元，包括苯酚环、噻吩环和正烷基链，通过C-C键和C-O键在分子间连接。[结论]快速连续分步热解技术在不同温度点获得的不同系列化合物分布及其变化有可能揭示藻类演化的细节并确定干酪根的不同有机质来源。
Abstract:
Abstract: [Objective] The Ordovician Kukersite oil shales that composed almost exclusively of Gloeocapsomorpha prisca (G. prisca) alginite are an important set Paleozoic source rocks from Paleozoic around the planet, but they have only been sporadically detected and reported in the Tarim Basin in China. Therefore, rapid identification of G. prisca in source rocks is an important geochemical work. Kerogen can be used to trace the source rock quickly for its enrichment of the parent material of hydrocarbon generation. [Method] Thus the kerogen from Estonian oil shale was analyzed using sequential stepwise pyrolysis with 50 °C intervals from 310 °C to 610 °C to investigate its chemical constitutions. [Results and discussion] The results illustrated that the pyrolyzed hydrocarbons formed upon sequential stepwise pyrolysis are dominated by 5-n-alkyl-1,3-benzenediols probably reflect a major contribution of selectively preserved, highly resistant biomacromolecules from the outer cell walls of G. prisca. It is also characterized by high content of short-chain alkanes, but abnormal high carbon number (>nC29) n-alkane/enes appear at 560 ℃. Besides, the consistent formation of alkyl benzenes, alkyl thiophenes and alkyl ketones also appeared at the middle to high temperature points (460 ~ 560 ℃). All pyrolyzates have the characteristics of lower carbon number, alkyl side chains with a distinct distribution of weak odd-over-even carbon numbers. The extremely abundant and continuous generation of 5-n-alkyl-1,3-benzenediols and its homologues in the pyrolysis products can help to quickly identify whether the source rocks contained G. Prisca or not. In addition, the composition characteristics, product changes and product correlation of the pyrolyzates at different temperatures are helpful for the investigation of kerogen structure. The results of sequential stepwise pyrolysis suggested that the macromolecules of kerogen were formed mainly by polymerization of 5-n-alkyl-1,3-benzenediols in G. prisca. The units in polymer macromolecules including phenol rings, thiophene rings, and normal alkyl chains, are intermolecular connected by C-C and C-O bonds. [Conclusions] The distribution changes of different series of compounds obtained at different temperatures by sequential stepwise pyrolysis can be applied to other organic-rich oil shales, which may reveal the details of algal evolution and determine the various sources of organic matter of kerogen.
点击查看大图
下载:
