This study aims to better understand the evolution of the organic matter (OM) ultrafine structure (designating the nanoscopic structure of the OM/macerals) and porosity with increasing thermal maturity of mudstones source-rocks. To this end, the particulate fractions of kerogen from organic-rich Kimmeridge clay mudstones were isolated by acidic treatment before and after laboratory thermal maturation. The evolution of the composition, the chemical structure and the porosity of kerogen from the immature stage (Ro = 0.42%) to the dry gas zone (Ro = 2.12%) were documented using a combination of elemental analysis, vitrinite reflectance measurements, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), Raman spectroscopy and Small Angle X-Ray Scattering (SAXS). The evolution of the porosity of OM was then compared to the evolution of the pore volume of the total rock measured by nitrogen adsorption. The results show that the progressive densification, reorganization and aromatization of the amorphous kerogen particles into a more ordered, but heterogeneous carbon-rich residue is responsible for significant variations in the kerogen porosity with increasing maturity. Contrary to the previous observations on these Kimmeridge clay mudstones, the variations that occur during the peak of oil generation (Ro of ca. 0.90%) mark the onset of the OM-hosted pores development. There appears to be a natural close relationship between the evolution of OM porosity and total pore volume of organic-rich mudstones during gas generation. Indeed, a similar alternation of pore collapse and pore development is observed in response to gas generation. The development and the evolution of pores in these organic-rich mudstones seems thus mainly driven by the evolution of the chemical structure and the composition of OM during thermal maturation. In the dry gas zone, the porosity and the specific surface area of the kerogen are significant (19% and 57.1 m2.g−2 respectively). This highlights the importance of the OM content, type and composition in the porosity and gas storage capacities of mudstone reservoirs, increasingly discussed in the available literature in recent years.

中文翻译：

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热成熟度对海相泥岩有机质超细结构和孔隙度伴随演化的影响；电子成像和新光谱研究的贡献

本研究旨在更好地了解有机质 (OM) 超细结构（指定 OM/微晶结构的纳米级结构）和孔隙度随泥岩烃源岩热成熟度的增加而演变。为此，在实验室热成熟之前和之后，通过酸处理分离了富含有机物的 Kimmeridge 粘土泥岩中干酪根的颗粒部分。使用元素分析、镜质体反射测量、扫描电子的组合记录了干酪根从未成熟阶段 (Ro = 0.42%) 到干气区 (Ro = 2.12%) 的组成、化学结构和孔隙度的演变显微镜 (SEM) 和透射电子显微镜 (TEM)、拉曼光谱和小角度 X 射线散射 (SAXS)。然后将 OM 孔隙度的演变与通过氮吸附测量的总岩石孔隙体积的演变进行比较。结果表明，随着成熟度的增加，无定形干酪根颗粒逐渐致密化、重组和芳构化成更有序但非均质的富碳残渣是干酪根孔隙度发生显着变化的原因。与之前对这些 Kimmeridge 粘土泥岩的观察相反，在生油高峰期间发生的变化（Ro 约为 0.90%）标志着 OM 赋存孔隙发育的开始。在天然气生成过程中，OM 孔隙度的演化与富有机质泥岩的总孔隙体积之间似乎存在着天然的密切关系。确实，观察到响应气体生成的孔隙坍塌和孔隙发展的类似交替。因此，这些富含有机质泥岩中孔隙的发育和演化似乎主要受热成熟过程中化学结构和 OM 组成的演化所驱动。在干气区，干酪根的孔隙度和比表面积显着（分别为 19% 和 57.1 m2.g-2）。这突出了 OM 含量、类型和成分在泥岩储层孔隙度和储气能力中的重要性，近年来在可用文献中越来越多地讨论。在干气区，干酪根的孔隙度和比表面积显着（分别为 19% 和 57.1 m2.g-2）。这突出了 OM 含量、类型和成分在泥岩储层孔隙度和储气能力中的重要性，近年来在可用文献中越来越多地讨论。在干气区，干酪根的孔隙度和比表面积显着（分别为 19% 和 57.1 m2.g-2）。这突出了 OM 含量、类型和成分在泥岩储层孔隙度和储气能力中的重要性，近年来在可用文献中越来越多地讨论。