未熟-低熟烃源岩的有机岩石学特征

采用全岩光片镜鉴和显微荧光分析方法 ,对我国不同地区 5 0 0余块未熟 低熟烃源岩样品进行了系统的有机岩石学研究。未熟 低熟烃源岩显微组分组成具有显著的非均质性 ,不同地区显示出陆源组分与水生生源组分不同的“配比”关系 ,反映出其有机质组成的复杂性 ,并确认藻类体、孢子体、树脂体、木栓质体、壳屑体和矿物沥青基质等组分是其最常见的生烃组分。基于对镜质组反射率Ro和孢子体荧光变化等演化指标特征的分析 ,认为未熟 低熟烃源岩有机质早期热演化具有明显的阶段性 ,一般都表现为“二段式”变化 ,其变化界限大致以Ro等于 0 .5 0 %～ 0 .5 5 %为界。

ORGANIC PETROLOGICAL CHARACTERISTICS OF IMMATURE SOURCE ROCKS

By using the analytical methods of determining macerals on whole rock polished surfaces and micro-fluorescence technique, a systematical study was conducted of organic petrology on more than 500 samples of immature source rocks ( Ro =0.21%-0.65%) from different areas in China. The immature source rocks consist of various macerals with obvious heterogeneity. Samples from different areas show differences in proportions between terrestrial macerals and hydrobiological macerals. Changes in proportions reflect the complexities of organic matter composition in immature source rocks. It is demonstrated that alginite, sporinite, resinite, suberinite, liptodetrinite and mineral bituminous groundmass are the most common hydrocarbon-generating macerals in immature source rocks. Based on the evolutionary characteristics of vitrinite reflectance ( Ro ) and sporinite fluorescence changes, it is suggested that early evolution of organic matter in immature source rocks is of obvious stage and generally shows a two-stage evolutionary pattern. There is a dividing line between the two stages around 0.5% to 0.55% Ro .