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扬子地区下寒武统广泛发育了1套黑色岩系,被认为是中国南方4套海相烃源岩之一。但由于该套烃源岩时代老、有机质成熟度高,故对其有机岩石学特征探讨还没有定论。通过光片、薄片的对比观察,结合扫描电镜和能谱等分析,详细研究了研究区下寒武统黑色岩系的有机岩石学特征,并尝试性地探讨了其油气地质意义。结果表明湘西三岔地区下寒武统黑色岩系中的有机质可划分为有形态组分、无形态组分。其中有形态组分又可分为植物藻类组(层状藻类体、结构藻类体Ⅰ、结构藻类体Ⅱ)、动物有机组、细菌型的菌类体及混合型海相镜质体;无形态组分主要为微粒体和沥青质体。从观察到的有机质组分反映了该套黑色岩系的生源母质具有多重属性,但从统计的各组分含量上来讲主要为浮游菌藻类、底栖宏观藻类、浮游动物和底栖海绵等,其有机质类型主要为Ⅰ型和Ⅱ型。系统的有机岩石学研究表明有机质差异主要是由母质类型的差异所造成,宏观底栖藻类和大型低等水生植物(如浅海底栖叶状体植物)的发育是形成Ⅱ型有机质的主要因素。对牛蹄塘组有机岩石学特征的分析为该套黑色岩系的油气生成潜力的研究提供了重要基础。
The Lower Cambrian extensively developed a series of black rock series in the Yangtze area and is considered as one of 4 sets of marine source rocks in southern China. However, due to the age of the source rocks of the set and the high maturity of organic matter, there is no conclusion about its organic petrological characteristics. The organic petrologic characteristics of the Lower Cambrian black rock series in the study area are studied in detail by comparing the light and thin sections with the scanning electron microscopy (SEM) and energy spectrum analysis. The petroleum geological significance is tentatively discussed. The results show that the organic matter in the Lower Cambrian black rock series in the Sancha area of western Hunan can be divided into morphological components and non-morphological components. Among them, the morphological components can be divided into plant algae group (phylloid body, structural algae body I, structural algae body Ⅱ), animal organism group, bacteria-type fungi body and mixed-type sea-phase vitrinite; The main components of microsomes and asphaltenes. The observed organic matter components reflect the multiple attributes of the parent material of the black rock series. However, the main components of the black rock series are planktonic algae, macro-benthic algae, zooplankton and benthic sponges, The organic matter types are mainly type I and type II. The systematic organic petrology study shows that the difference of organic matter is mainly caused by the difference of parent material types. The development of macrophytic benthic algae and large low-level aquatic plants (such as shallow-water benthic meristematic plants) is the main factor for the formation of type II organic matter. The analysis of the organic petrological characteristics of the Niutitang Formation provides an important basis for the study of the hydrocarbon generation potential of the black series.