显微组分荧光性变化——烃源岩有机质演化的一个重要方面

Fluorescence Alteration of Some Macerals——An Important Aspect of the Evolution of Organic Matters in Source Rocks

采用人工模拟热演化和地质热演化两个系列样品,研究了成熟作用对孢子体、藻类体等显微组分荧光性的影响。茂名油页岩从室温被加热至600℃的过程中,藻类体的荧光性在250℃～300℃发生突变,标志其化学结构中联系在芳香核上的各种官能团和脂族基团开始大量脱落,液态产物大量生成;之后,随着加热温度增高,藻类体荧光性消失,镜质体反射率猛增。伊敏盆地五牧场地区煤系烃源岩样品中,随成熟作用的增强,孢子体荧光光谱发生“红移”;同时,荧光强度衰减,这种变化与显微组分的成烃作用密切相关。在成熟作用初期,荧光光谱面貌的变化往往标志大量生油阶段的开始,而荧光的“淬灭”则与“液烃窗”的结束有关。上述研究表明,显微组分荧光性变化是烃源岩有机质演化的一个重要方面,它反映了显微组分化学结构变化和成烃作用的特征。

In this paper, some effects of the maturation on the fluorescences of alginites and sporinites are studied with both artificial simulation and natural evolution samples. When the Maoming oil shale is heated to 250-300℃, there are obvious changes in the nature of alginite fluorescence, which suggests that the chemical structure of alginite begins to lose alkyl chains and functional groups, and to generate liquid products. As the temperature goes up, the fluorescence would extinguish and the vitrinite reflectance would increase sharply. In a series of natural evolution samples, the spectral fluorescence of sporinites experiences 'red-shift' with maturity increasing, while the light intensities declines. Evidently, the changes are closely correlative to the hydrocarbon generation of the macerals. The beginning of the main oil generation phase is marked by the obvious alteration of spectral fluorescence pattern, while the end of'oil window' corresponds to the extinction of fluorescence. These observations lead to a conclusion that the fluorescence change is an important aspect of the thermal evolution of organic matters in the source rocks, and reflects the chemical structure evolution and hydrocarbon generation of the macerals.