Bitumen-bearing fractures and vugs were investigated in the highly organic-rich Jordan oil shale (JOS) of Late Cretaceous–Eocene age, which has potential as a highly fractured, unconventional hydrocarbon play. Bitumen is present as macroscopically visible deposits, and as inclusions in the cement of abundant natural fractures and adjacent vugs. The frequency of bitumen occurrence in fractures closely correlates with total organic carbon (TOC) and burial depth. Petrographical and organic-geochemical analyses on bitumen samples extracted from fractures and their host-rock matrix show that the fracture-filling bitumen comprises indigenous low maturity hydrocarbons derived from the surrounding organic-rich oil shale and has not migrated from a deeper source. Maturity indicators imply that the oil shale is in the pre-oil generation stage of early catagenesis throughout the investigated area, but with a regional increase in thermal maturity from west to east as the result of greater maximum burial depth. Bitumen mobilization in the host rock was mainly controlled by vertical loading stress acting on the non-Newtonian bitumen phase in load-bearing configurations in the organic-rich matrix. Bitumen fractures were developed by hydraulic fracturing as the result of fluid overpressure in the organic matter. Overpressured bitumen has acted as a fracture driver, generating bitumen veins in both the organic-rich mudstones and the adjacent chert and silicified intervals. Supplementary material: A summary of core data and photographs of the fracture bitumen and matrix bitumen are available at https://doi.org/10.6084/m9.figshare.c.4602290 Thematic collection: This article is part of the Naturally Fractured Reservoirs collection available at: https://www.lyellcollection.org/cc/naturally-fractured-reservoirs

中文翻译：

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沥青在早期退化过程中裂缝发育中的成因和作用

在晚白垩世-始新世的富含有机质的约旦油页岩 (JOS) 中研究了含沥青的裂缝和孔洞，该页岩具有作为高度裂缝性的非常规油气田的潜力。沥青以肉眼可见的沉积物和大量天然裂缝和相邻孔洞的水泥中的夹杂物形式存在。裂缝中沥青的出现频率与总有机碳 (TOC) 和埋藏深度密切相关。对从裂缝中提取的沥青样品及其寄主岩基质进行的岩石学和有机地球化学分析表明，裂缝填充沥青包含源自周围富含有机物油页岩的本土低成熟度碳氢化合物，并没有从更深的源头运移。成熟度指标表明整个调查区的油页岩处于早期后生作用的前生油阶段，但由于最大埋藏深度较大，热成熟度从西向东呈区域性增加。主岩中的沥青流动主要受垂直加载应力控制，该应力作用于富含有机物基质中承载配置的非牛顿沥青相。由于有机质中流体超压，通过水力压裂形成了沥青裂缝。超压沥青起到了裂缝驱动的作用，在富含有机质的泥岩和相邻的燧石和硅化层段中产生了沥青脉。补充材料：可在 https://doi.org/10 上获得裂缝沥青和基质沥青的岩心数据和照片摘要。