济阳坳陷中生界烃源岩生烃演化

济阳坳陷中生界油气藏发育,但至今尚未对中生界烃源岩的生烃演化进行过系统研究,影响了对该区中生界油气的勘探。对该区进行了地球化学数据分析,结果表明:济阳坳陷中生界下—中侏罗统坊子组主要为沼泽相的煤系烃源岩,总体评价为差—较好烃源岩,以生气为主;下白垩统蒙阴组以湖相泥岩为主,有机质类型好,达到中等—好烃源岩的标准,应以生油为主;下白垩统西洼组和中—上侏罗统三台组为差—非烃源岩。利用镜质体反射率(Ro)数据,结合构造演化史动态分析了中生界烃源岩在不同地质时期生烃演化过程。结论认为:研究区中生界有机质经历过两期成熟演化过程,济阳坳陷次级凹陷的中生界烃源岩的二次生烃门限深度介于3000～3700m;主要生烃演化过程发生在新生代,具有较大的油气资源潜力。研究成果为该区中生界下一步勘探目标的选择提供了依据。

Evolution of the Mesozoic source rocks in the Jiyang Depression

Although oil and gas reservoirs are well developed in the Mesozoic in the Jiyang Depression, no systematic study has been performed on the evolution of the Mesozoic source rocks till now, which impedes petroleum exploration in the Mesozoic in the study area. An analysis of geochemical data of the study area shows that the Lower Middle Jurassic Fangzi Formation of the Mesozoic in the Jiyang Depression is dominated by coal measure source rocks of paludal facies. They are poor to fair and gas prone source rocks as a whole. The Lower Cretaceous Mengyin Formation is dominated by lacustrine shale with favorable organic material type. They are moderate to good oil prone source rocks. The Lower Cretaceous Xiwa Formation and the Middle Upper Jurassic Santai Formation are poor source rocks or non source rocks. The evolution of the Mesozoic source rocks in different geologic times is studied by using the vitrinite reflectance (Ro) and in combination with tectonic evolutionary history. It is believed that the Mesozoic source rocks in the study area have experienced two stages of thermal evolution and the threshold of secondary hydrocarbon generation is 3000 ~ 3700 m for the Mesozoic source rocks in some sags of the depression. Peak hydrocarbon generation occurred in the Cenozoic `and the resource potential is large. These study results provide basis for the selection of future exploration targets in the Mesozoic of the study area.