成熟度对甾萜类化合物组成特征的影响--以银额盆地查干凹陷为例

Effects of maturity on the compositional characteristics of steranes and tepanes:a case study of Chagan Sag in Yin'gen-Eji'naqi Basin

采集银额盆地查干凹陷33个烃源岩样品、25个原油样品和32个油砂样品,进行饱和烃色谱质谱检测,分析不同成熟度样品中甾萜类化合物组成特征及变化规律。结果表明:随成熟度增大,研究区原油中三环萜烷、孕甾烷系列相对丰度升高,规则甾烷中C 29甾烷相对丰度降低、C27甾烷相对丰度升高,不同类型的原油表现不同的变化速率。查干凹陷K1b1烃源岩及生成的原油与K1b2的相比,三环萜烷、孕甾烷相对丰度较高,升高速率随成熟度增大而显著增大。三环萜烷和孕甾烷系列化合物相对丰度受控于有机质母质类型,在热演化过程中表现不同的演化规律;查干凹陷具有两种甾萜类生物标志化合物组合特征及演化模式的原油,分别来自K1b1和K1b2烃源岩。该结果对甾萜类生物标志化合物在油源对比应用中具有指导意义。

33 source rock samples,25 oil samples and 32 oil-bearing sand samples were collected from Chagan Sag in Yin'gen Basin.The saturated hydrocarbons were extracted from all the samples and then detected by GC-MS.The compositional characteristics and variation rules of steranes and tepanes in crude oil and soluble organic matter of source rocks with different maturity were analyzed in detail.The results show that,with the increase of maturity,the relative abundance of tricyclic terpenes and pregnanes gradually increase,the relative abundance of C29 steranes gradually decrease and that of C 27 steranes increase,however,different types of source rocks and their crude oils show different rates of change.Compared with K1b2 source rocks and correlated oil,K1b1 has the characteristics that the relative abundance of tricyclic terpenes and pregnanes are significantly higher,and the rate of increase with maturity is also significantly higher.It shows that the relative abundance of tricyclic terpenes and pregnanes compounds are based on the type of organic parent material,and shows different variation rules as the maturity increases.There are two biomarkers assemblage and evolution modes of crude oil in Chagan Sag,which are respectively from K1b1 and K1b2 source rocks.The results have important guiding significance for the application of steranes and terpenes biomarkers in oil-source correlation.