苏北盆地早第三纪烃源岩有机质热演化特征

Characteristics of Thermal Evolution of Organic Matter in Paleogene Source Rocks in Subei Basin

苏北盆地是一个较为复杂的断陷－坳陷型合油气盆地，对其早第二纪烃源岩有机质热演化程度的评价是目前尚未解决的课题。应用显微组分光学标志和可溶有机物化学标志，研究了苏北盆地早第三纪烃源岩有机质热演化特征、从而揭示了有机质热演化的不均衡性与阶段性。该盆地烃源岩的镜质组反射率Ｒｏ是最可靠的演化标志；孢子体和藻类体的荧光变化特征具有特殊重要的演化意义．正构烷烃分布特征和甾、藿烷异构体比值的演化趋势与显微组分的光性演化完全吻合。综合各种光学和化学标志，将苏北盆地有机质演化划分为阶段Ⅰ和阶段Ⅱ两个演化阶段，其阶段转折处的Ｒｏ在０．６０％～０．６５％之间。

The Subei basin is a relatively complicated faulted-depressed petroliferous basin, and assessment of thermal evolution level of organic matter in Paleogene source rocks in the basin is still unsolved.By using optical index of maceral and chemical index of soluble organic matter,the characteristics of thermal evolution of organicmatter from Paleogene source rocks in the Subei basin are studied systemically. A disequilibrium and stagging of thermal evolution are revealed. It is suggested that the vitrinite reflectance should be the most reliable indicator to represent thermal evolution level. Fluorescence alteration of sporinite and alginite shows a special significance for thermal evolution. The evolution characteristics of soluble organic matter are basically consistent with those of maceral. Through the comprehensive analysis, it is proposed that the evolution stage of organic matter in the Subei basin can be divided into stage.Ⅰand stage Ⅱ, and the transtion from stage Ⅰto stage Ⅱ occurs about 0.60%￣0.65% in vitrinite reflectance.