Organic petrology characteristics and occurrence of source rocks in Permian Lucaogou Formation, Jimsar sag

Key words:  organic petrology  maceral  source rock  Lucaogou Formation  Jimsar sag

Abstract:

Based on the core observation, thin section authentication and geochemical parameters analysis, the detailed study of organic petrology was conducted for the source rocks from the Permian Lucaogou Formation in Jimsar sag of the Junggar Basin. The modes of occurrence of organic matter in these source rocks were structrurally recognized as structural maceral, amorphous maceral, and secondary maceral with the aid of reflected and transmitted light petrography, the organic macerals mentioned above were divided into five groups (sapropelineie, exinite, vitrinite, inertinite, and secondary maceral) and further twelve sub-fractions, which was dominated by unstructural algae and asphaltene, the content of secondary macerals was generally higher, while the contents of vitrinite and inertinite were relative low and exinite occurred in minute amounts. According to the fluorescence, content and shape of organic maceral, the source rocks show strong heterogeneity in the types and contents of the components with respect to rocks types with various lithologies, textures and sedimentary structures. The total organic carbon contents and hydrocarbon generation potential are strongly correlated with the amount of unstructural algae and amorphous macerals, which suggests that unstructural algae and amorphous macerals are major components for the hydrocarbon generation in the Lucaogou Formation.