吉林市上二叠统杨家沟组烃源岩地球化学特征

Geochemical characteristics of source rocks from Upper Permian Yangjiagou Formation in Jilin City

通过对吉林市上二叠统杨家沟组烃源岩野外露头的系统采样,剖析烃源岩的地球化学特征,探讨烃源岩有机质的母质来源、沉积环境和热演化程度。研究表明,有机质母质来源既有高等植物的来源,还有细菌和藻类等低等水生生物的混入;具有典型湖相烃源岩的分布特征;烃源岩形成于半咸水还原的沉积环境,热演化程度为成熟-高成熟阶段。

Based on the GC- MS,the variation of organic matter origin,deposition environment and thermal maturity of hydrocarbon source rocks were systematically discussed. The distribution of tricyclic terpane is normal distribution with the main peak of C23,high content C24 tetracyclic terpane and a predominance of C27ααα20R sterane over C29ααα20R sterane with asymmetry＂V＂distribution indicates that the organic material of source rocks are higher terrigenous plants mixed with lower aquatic organisms. The main peak of hopanes is C30 hopane with the distribution of C31- C35 hopane decline as a ladder and the tricyclic terpane / hopane ratio is high shows the lacustrine facies characteristics.The Pr / Ph value（ 0. 44 ~ 0. 49） and gammacerane / C30 hopane value（ 0. 32 ~ 0. 38） indicate that source rocks are developed in brackish water reductive semideep- deep lake environment. The maturity parameters of C29ααα20S /（ 20 S ＋ 20R）,C29αββ /（ ααα ＋ αββ） and C31αβ22S /（ 22 S ＋ 22R）have reached the balanced endpoint value of isomerization,indicating the source rocks stay in mature- high mature stage during the thermal evolution.