Geological models for petroleum generation suggest thermal conversion of oil-prone sedimentary organic matter in the presence of water promotes increased liquid saturate yield, whereas absence of water causes formation of an aromatic, cross-linked solid bitumen residue. To test the influence of hydrogen from water, organic-rich (22 wt% total organic carbon, TOC) mudrock samples from the Eocene lacustrine Green River Formation Mahogany zone oil shale were pyrolyzed under hydrous and anhydrous conditions in closed system batch reactors at temperatures between 300 and 370 °C for 72 h. Pre- and post-pyrolysis samples were characterized using petrographic approaches including optical microscopy, reflectance, Raman spectroscopy, and scanning electron and transmission electron microscopy to quantify differences in relative appearance, abundance, and composition of solid bitumen newly generated during the pyrolysis experiments. Petrographic analyses were supplemented by geochemical screening measurements (TOC content and programmed temperature pyrolysis). Results show post-hydrous pyrolysis residues contain lower TOC, are comprised of solid bitumen with greater aromaticity, and have textures indicative of lower viscosities, relative to anhydrous residues from the same temperature pyrolysis conditions. These observations suggest solid bitumen forming from thermal conversion of oil-prone sedimentary organic matter under anhydrous conditions may be less aromatic, although more cross-linked, than solid bitumen forming under hydrous conditions at the same time-temperature combination. To explain these results, we suggest that a radical disproportionation mechanism is favored in the presence of hydrogen donated from water, and that this disproportionation promotes aromatization in the solid residue with concomitant expulsion of saturated hydrocarbons.

石油生成的地质模型表明，在有水存在的情况下，易产油的沉积有机质的热转化促进了液体饱和产量的增加，而没有水则导致形成芳香的、交联的固体沥青残渣。为了测试来自水中的氢的影响，来自始新世湖泊绿河组桃花心木带油页岩的富含有机物（22 wt% 总有机碳，TOC）泥岩样品在封闭系统间歇式反应器中的含水和无水条件下，温度介于300 和 370 °C 72 小时。使用包括光学显微镜、反射率、拉曼光谱、扫描电子和透射电子显微镜在内的岩相学方法对热解前后样品进行表征，以量化相对外观、丰度、以及热解实验中新产生的固体沥青的组成。岩石学分析由地球化学筛选测量（TOC 含量和程序温度热解）补充。结果表明，与来自相同温度热解条件的无水残渣相比，含水热解残渣含有较低的 TOC，由具有更高芳香性的固体沥青组成，并且具有表明粘度较低的质地。这些观察结果表明，在无水条件下由易产油沉积有机质热转化形成的固体沥青可能比在相同时间-温度组合下的含水条件下形成的固体沥青芳香性更低，尽管交联度更高。为了解释这些结果，