洪泽凹陷低熟原油的饱和烃化合物组合

Biomarker Assemblage of Immature Oils in Hongze Sag, Subei Basin, East of China

通过对洪泽凹陷低熟原油中饱和烃化合物组合研究表明，它们能够较为有效和准确地确定低熟原油的生烃母质和沉积环境。在洪泽凹陷原油中，存在着典型半咸水—咸水环境的生物标志物组合，如Ｐｒ／Ｐｈ＜１，丰富的伽玛蜡烷，相对较高含量的Ｃ２９４－甲基甾烷，Ｃ２６甾烷，甲藻甾烷等。虽然洪泽凹陷具有近物源的沉积特征，但原油中的化合物组合仍表明半咸水—咸水环境的菌藻类微生物是低熟油的重要生烃母质。原油中高丰度的ｎＣ２２或ｎＣ２３正构烷烃，异构、反异构烷烃，Ｘ化合物，长链类异戊二烯烷基苯、甲藻甾烷等化合物的检出均证实这种生源输入的贡献。同时，原油中还检测到Ｃ３０未知三萜烷（ｕｃＴ）的存在。

Biomarker assemblage of Hongze crude oils shows that the hydrocarbons constitution can provide very useful and accurate information about the precursor, origin and sedimentary environment of the immature oils.The oils have a typical biomarker assemblage of brackish-saline environments, for example, Pr/Ph<1, high concentration of gammacerane, relatively higher amounts of 4-methyl C 29 sterane (C 29 >C 28 , C 30 ), identification of C 26 sterane and dinosterane etc.. Through the Hongze sag is near the provenance and has higher plant source input, microbes (algae and bacteria) in brackish -saline environments are still the most important precursor of the immature oils. The predominace of nC 22 , nC 23 , n-alkanes and distribution of isoalkanes, anti-isoalkanes, Ⅹ compounds, long-chain isoprenoids alkylbenzene series, dinosterane etc. have verified this kind of assumption. Meanwhile, the existence of C 30 ucT (unconfirmed triterpane) also indicates that there are some special organisms related to the immature oil formation. Some other geochemical characteristics of the oils are also disscussed herein.