羌塘盆地中央隆起带下二叠统展金组烃源岩芳烃化合物特征研究

Study on Characteristics of Aromatic Compounds in Source Rocks of Lower Permian Zhanjin Formation in the Central Uplift of Qiangtang Basin

利用芳烃化合物抗风化、抗生物降解能力强的特点,采用色谱-质谱分析技术,对羌塘盆地中央隆起带展金组烃源岩的芳烃地球化学特征进行分析研究。在检测出的芳烃化合物中,以菲系列为优势主分,其次为三芴系列、萘系列以及联苯系列等,芳烃化合物分布具有较明显的前锋型特征。根据芳烃化合物组成以及相对丰度,认为展金组烃源岩的有机质主要来源于低等水生生物,但联苯系列、荧蒽、芘、苝系列等化合物的检出,表明陆源植物对有机质的来源也有贡献。菲系列化合物的高含量、芴系列相对含量占优势以及沉积环境判别图等,综合显示出烃源岩形成于还原条件下的海相环境。利用MNR、DNR1、Rca、TNR1、TNR2、Rcb、Rc、Ro(K4,6,%)、Ro(K2,4,%)等多个指数对烃源岩成熟度进行判断,认为烃源岩达到成熟阶段,未达到高成熟阶段,这与实测Ro值所吻合。

Based on the characteristics of strong weathering and biodegradation resistance of aromatic compounds,aromatic geochemical characteristics of Zhanjin Formation source rocks in the central uplift of Qiangtang basin are analyzed and studied by chromatographymass spectrometry.Among the detected aromatic compounds,phenanthrene series is the dominant main component,followed by trifluorene series,naphthalene series and biphenyl series.The distribution of aromatic compounds has obvious forward characteristics.According to the composition and relative abundance of aromatic compounds,it is considered that the organic matter of the source rocks of Zhanjin Formation mainly comes from lower aquatic organisms,but the detection of biphenyl series,fluoranthene,pyrene and perylene series shows that terrestrial plants also contribute to the formation of source rocks.Higher phenanthrene series compound content,the dominant relative content of fluorene and the discrimination map of sedimentary environment show that the source rocks were formed in the marine environment under the condition of reduction.Using MNR,DNR1,Rca,TNR1,TNR2,Rcb,Rc,Ro(K4,6,%),Ro(K2,4,%)and other indexes to judge the maturity of source rocks,it is considered that the source rocks have reached the mature stage but not reached the high mature stage,which is consistent with the measured Ro value.