Thermal maturity is commonly assessed by various geochemical screening methods (e.g., pyrolysis and organic petrology). In this contribution, we attempt to establish an alternative approach to estimating thermal maturity with Raman spectroscopy, using 24 North American oil shale samples with thermal maturity data generated by vitrinite reflectance (VR_o%) and pyrolysis (T_max)-based maturity calculation (VR_e%). The representative shale samples are from the Haynesville (East Texas), Woodford (West Texas), Eagle Ford and Pearsall (South Texas) Formations, as well as Gothic, Mancos, and Niobrara Formation shales (all from Colorado). The Raman spectra of disordered carbonaceous matter (D1 and G bands separation) of these samples were directly obtained from the rock chips without prior sample preparation. Using the Gaussian and Lorentzian distribution approach, thermal maturities from VR were correlated with carbon G and D1. We found that the Raman band separation (RBS) displayed a better correlation for equivalent VR_e% than vitrinite reflectance VR_o%. The RBS (D1–G) distance versus total organic carbon, free hydrocarbons from thermal extraction (S1), and the remaining hydrocarbon generating potential (S2) indicate that the RBS (D1–G) distance is also related to kerogen type. Data presented here from three methods of maturity determination of shale demonstrate that Raman spectroscopy is a quick and valid approach to thermal maturity assessment.

中文翻译：

---

拉曼光谱法对美国油页岩样品的热成熟度评估：与镜质体反射率和热解方法的比较

通常通过各种地球化学筛选方法（例如热解和有机岩石学）评估热成熟度。在此贡献中，我们尝试使用拉曼光谱法建立估计热成熟度的替代方法，使用24个北美油页岩样品，其热成熟度数据由镜质体反射率（VR _o％）和热解（T _max）计算得出（ VR _è％）。代表性的页岩样品来自海恩斯维尔（东德克萨斯），伍德福德（西德克萨斯），伊格福特和皮尔索尔（南德克萨斯）地层，以及哥特，曼科斯和尼布拉拉组页岩（均来自科罗拉多州）。这些样品的无序碳质物质（D1和G谱带分离）的拉曼光谱直接从岩屑中获得，而无需事先准备样品。使用高斯和洛伦兹分布方法，VR的热成熟度与碳G和D1相关。我们发现拉曼能带分离（RBS）对等效VR _e％的显示比镜质体反射率VR _o更好的相关性％。RBS（D1-G）距离与总有机碳，热萃取产生的游离烃（S1）和剩余的生烃潜力（S2）的关系表明，RBS（D1-G）距离也与干酪根类型有关。从三种确定页岩成熟度的方法中得出的数据表明，拉曼光谱法是一种快速有效的热成熟度评估方法。