晋县凹陷下第三系沙四段至孔一段甾烷高异构化程度及未熟油形成机理探讨

A study on the origin of high maturity of steranes and the generation of immatur e oil from Paleogene in Jinxian sag.

通过冀中地区晋县凹陷下第三系沙四段至孔一段14口井 30块样品的色谱质谱分析 ,鉴定出 15个系列182个生物标志物。研究不同沉积环境下生物标志物的组合特征及其地质意义 ,讨论该层段盐湖相烃源岩甾烷“熟化”现象的产生及未熟油的生成 ,认为 :①水介质化学条件的变化是决定晋县凹陷中南部该层段三角洲相沉积中生物标志物组合特征多样性的重要因素 ;②该层段盐湖相未熟沉积有机质中存在的甾烷“熟化”现象 ,是由于在咸化水介质化学条件下 ,ββ 构型甾烷由甾醇经甾烯中间产物的还原作用而生成这一生成机理所引起的 ;③ββ 构型甾烷既可能具有热力学效应 ,也可能具有沉积环境的指相意义 ;④从一些生物标志物的生成机理和演化途径看 ,该凹陷未熟油可能是在咸化程度较高的水介质条件下 。

biomarkers in 15 series have been identified from 30 samples of 14 wel ls by GC MS analysis. They are all from the Paleogene in Jinxian sag of Jizhong area. Studies on their combination in d ifferent sedimentary environments and the significance as well as the origin of high maturity of steranes in the salt lake environment and the generation of imm ature oil indicate that (1)the change of hydrochemical characteristics is the i mportant factor that leads to different occurrences of biomarkers in the sedimen ts of deltaic facies of Paleogene in the Jinxian sag; (2)the origin of high matu rity of steranes in the salt lake environment of the Jinxian sag is the result o f that 14β(H),17β(H) steranes generated from sterols and though steranes gene rated under the hypersaline hydrochemical characteristics; (3)14β(H),17β(H) s teranes is not only the products of the thermodynamic effect, but also the indi cant of the sedimentary environment; and (4) generation mechanisms of some bioma rk ers have showed in this paper that the immature oil is the product of the chemic al and biochemical reaction under the low temperature and hypersaline hydrochemi cal characteristics.