Nanoscale geochemical heterogeneity of organic matter in thermally-mature shales: An AFM-IR study
Nanoscale geochemical heterogeneity of organic matter in thermally-mature shales: An AFM-IR study
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DOI：
10.1016/j.fuel.2021.122278
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发表时间：
2022
期刊：
影响因子：
7.4
通讯作者：
Ke Wang;Lin Ma;K. Taylor
中科院分区：
文献类型：
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作者：
Ke Wang;Lin Ma;K. Taylor
页岩中有机质的组成和特征可以揭示成岩过程中油气生成、运移和聚集过程的重要信息。它还可能影响页岩的化学性质和力学行为，页岩充当碳气藏或碳和地下能量储存的盖层/封闭层。在这里，我们应用先进的基于原子力显微镜的红外光谱(AFM-IR)来捕捉单个有机粒子纳米级分子组成的化学结构，并无损地绘制典型官能团的分布图；这是传统分析方法无法实现的，因为有些方法会损坏样品，有些方法只能收集大量测量数据，有些方法无法达到纳米级分辨率。比较了立陶宛波罗的海盆地页岩和英国鲍兰页岩的AFM-IR热成熟样品中有机质的纳米尺度地球化学特征。在迁移的固体沥青中可以观察到显著的化学不均一性。相比之下，笔石、褐藻土和惰质组的分子组成一般都是均一的。薄层作为碳氢化合物垂直迁移障碍的潜在作用也是显而易见的。这项研究提供了有关热成熟页岩中不同有机质类型的纳米尺度地球化学信息，以加深对有机质在排烃和运移过程中分子结构变化的理解，并揭示了纳米地球化学对提高天然气采收率、碳封存和地下储氢相关能源应用的影响。我们还使用AFM-IR表征了其他地质学研究中未报道的特定材料。其中一些与样品中的其他有机物颗粒表现出相似的特征，但不排除在样品储存或制备阶段引入未知有机污染物的可能性。对这种未定义的有机材料进行了全面的分析。未来的研究需要在样品制备和储存过程中采用标准化方法，以清除潜在的表面附着污染物。
The composition and characteristics of organic matter within shales can reveal important information on hydrocarbon generation, migration and accumulation processes during catagenesis. It may also impact upon the chemical properties and mechanical behavior of shales acting as hydrocarbon reservoirs or caprocks/seals for carbon and subsurface energy storage. Here we apply advanced atomic force microscopy-based infrared spectroscopy (AFM-IR) to capture thein-situchemical structure of nanoscale molecular composition of individual organic particles and map the distribution of typical functional groups nondestructively; something that cannot be achieved via conventional analysis since some methods damage the sample, some only collect bulk measurements and some do not achieve nano-scale resolution. The nanoscale geochemical characteristics of organic matter in thermally mature samples of a Baltic Basin shale, from Lithuania and the Bowland Shale, from the UK, obtained from AFM-IR, are compared in this study. Significant chemical heterogeneity can be observed in migrated solid bitumen. In contrast, graptolite, alginite and inertinite generally display homogeneous molecular composition. The potential role of laminae as barriers to the vertical migration of hydrocarbons is also apparent. This research provides insights into nanoscale geochemical information on different organic matter types in thermally-mature shales to enhance the understanding of molecular structure transformation of organic matter during hydrocarbon expulsion and migration processes, and also sheds light on implications of nanogeochemistry for enhanced gas recovery, carbon sequestration and underground hydrogen storage-related energy applications. We also characterised specific materials which have not been reported in other geological studies using AFM-IR. Some of them display similar characteristics to other organic matter particles in the samples, but the possibilities of unknown organic contaminants introduced to the sample during sample storage or preparation stages cannot be ruled out. A comprehensive analysis on this undefined organic material is provided. Standardized approaches during sample preparation and storage are required for future research to dislodge potential surface-attached contaminants.