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Bongro盆地西部地区勘探程度低,对其含油气前景认识有限。利用西部凹陷2口探井烃源岩样品的有机地球化学分析资料,结合区域地质资料,从烃源岩生烃潜力、生烃史以及生物标志化合物特征等方面,对Bongor盆地西部凹陷下白垩统K组烃源岩地球化学特征进行综合研究。结果表明:西部凹陷K组地层暗色泥岩、页岩发育;烃源岩有机质丰度高,整体评价为好烃源岩;有机质类型好,主要为Ⅱ1型有机质;K组下部烃源岩处于成熟热演化阶段,K组上部烃源岩处于低成熟热演化阶段。生烃史模拟表明,K组下部烃源岩分别于早白垩世晚期和晚白垩世早期进入生烃门限和成熟热演化阶段,而K组上部烃源岩在地质历史时期一直没有进入成熟热演化阶段,现阶段处于低成熟阶段。烃源岩饱和烃生物标志化合物特征表明,K组烃源岩形成于半咸水—淡水、弱氧化—弱还原的湖相沉积环境,其有机质组成为典型的湖相混合型有机质特征。
The exploration in the western Bongro Basin is low and its understanding of the hydrocarbon-rich future is limited. Based on the data of organic geochemical analysis of two exploration wells in western sag, combined with the regional geological data, the hydrocarbon generation potentials, hydrocarbon generation history and characteristics of biomarkers from the source rocks were studied in K group Geochemical characteristics of source rocks for a comprehensive study. The results show that there are dark shales and shales in Group K of the western depression. The source rocks are high in organic matter abundance and are generally evaluated as good source rocks. The organic matter types are good and are mainly Type II1 organic matter. The source rocks in the lower K group are in mature heat In the evolutionary stage, the Upper K-Group source rocks are in the stage of low-maturity thermal evolution. Hydrocarbon generation history shows that the source rocks in the lower K group entered the hydrocarbon generation threshold and mature thermal evolution stages in the early Early Cretaceous and early Late Cretaceous, respectively, whereas the upper K source rocks did not enter the mature thermal evolution during geological history Stage, the current stage is in a low stage of maturity. The characteristics of biomarker compounds of hydrocarbon saturated hydrocarbon indicate that source rocks of K group formed in lacustrine sedimentary environment of brackish water - freshwater, weak oxidation - weak reduction, and the organic matter composition of the K group is typical mixed organic matter of lacustrine facies.