泥页岩不同介质中可溶有机质组成差异性及对页岩油富集的意义

泥页岩中的有机质组成复杂，其差异性对于认识油气的生排烃和页岩油气的形成与富集机理具有重要意义。选择南襄盆地泌阳凹陷始新统核桃园组湖相泥页岩为研究对象，系统对比了其中不同介质（包括无机矿物和有机干酪根）中可溶有机质的组成与差异，并与页岩油和砂岩油相对比，分析差异性，讨论其地质地球化学意义。结果表明，泥页岩不同介质中可溶有机质的饱和烃组成差异性较小，难以区分，反映了页岩油气的源内生排烃过程，饱和烃自身各种化合物之间的极性差异不大；而芳烃组成差异明显，其中，有机介质中可溶有机质的芳烃组成与页岩油/砂岩油相当，而无机介质中可溶有机质的芳烃组成与页岩油/砂岩油差异较大，反映了油气生排烃的过程。据此，泥页岩在初次运移的排烃过程中，生成的烃类物质首先充满无机矿物基质孔隙，并满足矿物颗粒表面吸附后，进入烃源层内微裂缝和/或砂岩夹层而富集，这类油气资源即目前所谓的页岩油。 

Composition difference of soluble organic matter in different media in mudstones and its significance for shale oil enrichment

The composition of soluble organic matter in mudstones is complex and the study of composition diffe-rence is not only important to understanding hydrocarbon generation and expulsion processes, but also necessary for us to determine shale oil formation and accumulation mechanisms. Lacustrine shale of the Hetaoyuan Formation in the Biyang Sag of Nanxiang Basin was systematically studied to determine the composition difference of soluble organic matter from different media (including inorganic minerals and kerogen). The results were compared with shale oil and sandstone oil, and their geological and geochemical significance discussed. Results show that, it is mainly because of the similar polarity among various compounds of saturated hydrocarbon that we can hardly distinguish the difference of saturated hydrocarbon component of soluble organic matter in different media, which implies shale oil generation and expulsion processes in source rock. However, there are obvious variations of aromatic composition. The aromatic composition of soluble organic matter in organic medium is similar to shale oil/sandstone oil, but the aromatic composition of soluble organic matter in inorganic medium is different from shale oil/sandstone oil, which reflects the processes of hydrocarbon generation and expulsion. Accordingly, in the primary migration in mudstone, the generated hydrocarbons firstly filled inorganic mineral pores, after achieving the adsorption capacity of mineral particles, then entering into the micro-cracks in source rock and/or sandstone interlayer, finally forming oil and gas enrichment, which was the so-called shale oil.