松辽盆地上二叠统林西组烃源岩地球化学特征

The Geochemical Characteristics of Source Rocks of Upper Permian Linxi Formation in Songliao Basin

通过对钻遇松辽盆地上二叠统林西组烃源岩各井的岩心采样,在进行有机碳测试、全岩显微组分、镜质体反射率等常规地球化学分析的基础上,运用气相色谱和色谱-质谱联用分析技术,剖析了烃源岩的地球化学特征,探讨了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,烃源岩有机质丰度较高,有机质类型为Ⅲ,处于高-过成熟阶段,以生气为主,但现今生烃潜力有限;C_(27)、C_(28)和C_(29)ααα20R甾烷呈近"V"字形分布,表明有机质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,为混合型母质。烃源岩中三环萜烷呈以C23为主峰碳的似正态分布,藿烷以C30藿烷为主峰,C31~C35升藿烷系列化合物含量呈阶梯状依次递减,三环萜烷/藿烷比值较高,具有典型湖相烃源岩的分布特征。Pr/Ph和伽马蜡烷/C_(30)藿烷分别为0.30~0.67和0.32~0.39,反映烃源岩形成于半咸水还原的沉积环境。成熟度参数C29ααα20S/(20S+20R)、C29αββ/(ααα+αββ)和C31αβ22S/(22S+22R)均到达异构化终点的平衡值,与Ro结果相符,说明烃源岩热演化程度为成熟-高成熟阶段。

Based on the analysis of organic carbon content, whole rock macerals and vitrinite reflectance measure- ment, combined with GC and GC-MS, the variation of organic matter origin, deposition environment and thermal maturity of hydrocarbon source rocks from the Upper Permian Linxi formation in Songliao basin have been systemat- ically discussed. The results showed that the organic matter abundance are high and thermal evolution are in a high mature stage with type lI[ kerogen. The source rocks mainly generate gas and the hydrocarbon-generating potential are limited. The distribution of C27, C28, C29 ααα20R sterane is asymmetry ＂V＂ indicates that the organic material of source rocks are higer terrigenous plants mixed with lower aquatic organisms. The main peak o{ hopanes is C30 ho- pane with the distribution of 31 -C35 hopane decline as a ladder and tricyclic terpane/hopane ratio is high shows the lacustrine facies characteristics. The Pr/Ph value （0.30-0.67） and gammacerane/C30 hopane value （0.32--0.39） indicate that source rocks are developed in brackish water reductive environment. The maturity parameters of C29 ααα20S/（20S＋ 20R）, C29 αββ/（ααα＋αβ） and C31αβ22S/（22S＋ 22R） have reached the balanced endpoint value of isomerization, indicating the source rocks stay in mature-high mature stage during the thermal evolution consistentv.）ith R,, results.