摘要
氮同位素的分布特征在古气候环境、古沉积及演化特征的研究方面具有重要的意义。氮是原油的重要元素之一,主要赋存于非烃和沥青质组分中,按极性可划分为碱性和非碱性含氮组分。由于原油的碳/氮比高,大部分原油无法通过直接测试获得稳定的氮同位素数据,从而制约了原油氮同位素数据的分析与应用。为了解决原油氮同位素实验测试技术瓶颈,更好地推动原油氮同位素的科学研究与生产应用,本文利用两阶段分离的前处理方法,首先将原油中的非烃和沥青质组分进行分离,并在非烃组分中分离出碱性氮和非碱性氮组分。采用杜马斯燃烧法对原油中的各含氮组分进行同位素测定;同时选用不同值域范围的多个稳定氮同位素标准样品(USGS61、USGS62、USGS63)对实验数据结果进行质量监控,原油各组分氮同位素数据不确定度均小于±0.4‰。通过分离、测定海相和陆相两种不同沉积环境的原油样品,结果表明:陆相沉积环境的原油样品氮同位素重于海相沉积环境;沥青质组分氮同位素分布范围(δ^(15)N沥-海=3.0‰~5.5‰;δ^(15)N沥-陆=7.4‰~9.4‰)重于非烃组分(δ^(15)N_(非-海)=2.1‰~3.3‰;δ^(15)N非-陆=3.8‰~5.4‰);不同极性含氮化合物的氮同位素的分布特征表现为非碱性氮组分(δ^(15)N_(非碱-海)=2.5‰~3.2‰;δ^(15)N非碱-陆=5.9‰)重于碱性氮组分(δ^(15)N碱-海=0.8‰~1.0‰;δ^(15)N碱-陆=3.5‰)。
BACKGROUND:The distribution of nitrogen isotopes has important significance in paleoclimate,paleo-sedimentary and evolutionary characteristics.Nitrogen is one of the important heteroatomic elements in crude oil.The nitrogen content of crude oil is generally 0.1%to 2%,mainly in the non-hydrocarbon and asphaltene fractions,and can be divided into basic and non-basic nitrogenous fractions according to polarity.Due to the high carbon/nitrogen ratio of crude oils,accurate nitrogen isotope analysis results cannot be obtained from direct testing for most crude oils.As a result,the research on nitrogen isotopes in crude oil has been developed slowly,and the available data are few,while not being well applied in practice.OBJECTIVES:To determine the nitrogen isotopic distribution characteristics of different nitrogen-containing components in crude oil,and to address the problem of low nitrogen content in crude oil,which makes the direct determination of nitrogen isotopes less stable and reproducible.METHODS:A two-stage separation pre-treatment method was utilized to successively separate the non-hydrocarbon and asphaltene fractions of crude oil,and the basic and neutral nitrogen fractions were separated from the non-hydrocarbon fraction.The characteristics of nitrogen isotope distribution in different nitrogenous components of crude oil were determined by the Dumas combustion method.Multiple stable nitrogen isotope standards(USGS61,USGS62,USGS63)were selected for quality control of nitrogen isotope results.RESULTS:The nitrogen isotope data obtained by this method for each component of crude oil were of good quality,with the uncertainties less than±0.4‰.By separating and measuring crude oil samples from marine and continental sedimentary environments,the results showed that the nitrogen isotope of crude oil samples in continental sedimentary environment was heavier than that in a marine sedimentary environment.The distribution of nitrogen isotopes of asphaltene fractions was heavier than that of non-hydrocarbon fractions.The distribution characteristics of the nitrogen isotopes of the different polar nitrogen-containing compounds also differed significantly.CONCLUSIONS:The technical dilemma that crude oil samples cannot accurately produce stable nitrogen isotopes due to the disparity in carbon to nitrogen ratios is solved and technical support for the practical application of a crude oil nitrogen isotope index is also obtained.
作者
栗敏
秦婧
白杨
何晨
徐学敏
陈践发
LI Min;QIN Jing;BAI Yang;HE Chen;XU Xuemin;CHEN Jianfa(National Research Center for Geoanalysis,Beijing 100037,China;Chinese Academy of Geological Sciences,Beijing 100037,China;College of Geosciences,China University of Petroleum,Beijing 102249,China;College of Chemical Engineering and Environment,China University of Petroleum(Beijing),Beijing 102249,China)
出处
《岩矿测试》
CAS
CSCD
北大核心
2023年第4期771-780,共10页
Rock and Mineral Analysis
基金
国家自然科学基金青年科学基金项目“泥页岩中不同赋存状态氮同位素分布特征及其地质意义”(41902159)。
关键词
原油
氮同位素
含氮组分
杜马斯燃烧法
crude oil
nitrogen isotopes
nitrogenous components
Dumas combustion method