Nitrogen isotopes of marine oils in the Tarim Basin,China:Implications for the origin of organic matters and the paleoenvironment  

作　　者：Yang Bai Jian-Fa Chen Wen-Zhe Gang Xin-Jian Zhu Vaclav Suchy Shuai-Qi Tang Jin Wu Min Li Sheng-Bao Shi 

机构地区：[1]National Key Laboratory of Petroleum Resources and Engineering,China University of Petroleum(Beijing),Beijing,102249,China [2]College of Geoscience,China University of Petroleum(Beijing),Beijing,102249,China [3]PetroChina Hangzhou Research Institute of Geology,Hangzhou,310023,Zhejiang,China [4]Nuclear Physics Institute,v.v.i.,Academy of Sciences of the Czech Republic,Na Truhlarce 39/64,18086 Prague 8,Czech Republic [5]Chinese Academy of Geological Sciences,Beijing,100037,China

出　　处：《Petroleum Science》2024年第6期3692-3705,共14页石油科学(英文版)

基　　金：financially supported by the National Natural Science Foundation of China(No.41972127);the National Key Research and Development Program of China(No.2021YFA0719000)。

摘　　要：Nitrogen isotope compositions(δ15N)of sedimentary rocks are usually used to reconstruct the paleoenvironment and nitrogen(N)biogeochemical cycle.Theδ15N values of crude oils inherit the characteristics of relevant source rocks and can well reflect the information of hydrocarbon-forming organisms and environment in ancient water column.However,studies on theδ15N of crude oils are limited due to the low N content.In this study,a new efficient method is applied to the marine oils from the Bashituo(BST)and Halahatang(HLHT)areas of the Tarim Basin to obtain the nitrogenous components(i.e.,nonhydrocarbons and asphaltenes)for the achievement of N concentration.The carbon and nitrogen isotopes of these components and the biomarkers of oils were measured.Theδ15N values in asphaltenes(δ15NAsp)are significantly heavier than those in nonhydrocarbons(δ15NNSOs)in these oils,which are attributed to the potential directional N transfer and kinetic isotope fractionation during the thermal evolution of organic matters(OM).Theδ15NAspvalues have significant correlations with OM origin associated parameters and weak correlations with environmental parameters,suggesting that the difference inδ15NAspvalues is mainly resulted from biological source rather than redox conditions.Theδ15NNSOsvalues have a closer relationship with the redox condition than biological characteristics,indicating that they have a good response to paleoenvironmental variation in the water column,which is not completely overprinted by the difference of OM origin.Different redox conditions give rise to distinct nitrogen cycles,resulting in variousδ15N values.Anammox occurs in the water column of the Early Cambrian dominated by physically stratified conditions with significant isotope fractionation,resulting in relatively heavierδ15N of OM in the BST area.In the Middle-Late Ordovician period,the limited suboxic zone leads to an insignificant positive bias ofδ15N caused by partial denitrification in the HLHT oils.The evaluation ofδ15N in nitrogenous frac

关 键 词：Nitrogen isotope Nitrogenous components Crudeoils Organic matter Redox conditions Nitrogen cycle 

分 类 号：TE311[石油与天然气工程—油气田开发工程]