摘要
氮作为重要的生命元素与有机质聚集之间具有成因联系,但尚未形成系统性、规律性认识。以中国广泛发育的二叠系—古近系陆(湖)相烃源岩为例,对此进行了探讨。结果表明,根据氮同位素(δ^(15)N)组成,结合盐度和蒸发性碱类矿物特征,可将中国陆相烃源岩分为3组:近中性组1(δ^(15)N平均值为4.0‰±1.5‰)、近中性组2(δ^(15)N平均值为7.1‰±1.6‰)和碱性组(δ^(15)N平均值为18.4‰±3.3‰)。在δ^(15)N<10‰的近中性组中,烃源岩的δ^(15)N与有机质丰度、类型、生烃能力和页岩油潜力呈正相关,原因在于较高的δ^(15)N值指征了生烃母质组成的变化。在δ^(15)N>10‰的碱性组中,有机质类型都较好,页岩油潜力都较高,但烃源岩的δ^(15)N与有机质聚集的响应关系不如中性组,反映有机质聚集受非δ^(15)N其他综合因素的影响与控制。据此建立了基于δ^(15)N划分出的3类湖相烃源岩的有机质聚集模式(<5‰、5‰~10‰、>10‰)。δ^(15)N具有示踪有机质聚集和烃源岩质量的潜力,以湖相烃源岩为例,低δ^(15)N型(δ^(15)N<5‰)质量差,中—高δ^(15)N型(δ^(15)N>5‰)质量好。从氮同位素组成和氮循环这一新角度探讨了烃源岩有机质聚集,丰富了氮的生物地球化学与烃源岩地球化学研究。
As an important biological element,nitrogen is causally linked with organic matter accumulation,but a systematic and regular understanding has not been developed.This paper discusses this issue by taking the widely developed Permian-Paleogene terrestrial(lacustrine)hydrocarbon source rocks in China as an example.The results show that the terrestrial source rocks in China can be classified into three groups according to the nitrogen isotope(δ^(15)N)compositions and combined with the salinity and evaporative alkali mineral characteristics:the circum-neutral group 1(averageδ^(15)N=4.0‰±1.5‰),the circum-neutral group 2(averageδ^(15)N=7.1‰±1.6‰),and the alkaline group(averageδ^(15)N=18.4‰±3.3‰).In the circum-neutral group withδ^(15)N<10‰,theδ^(15)N of the source rocks is positively correlated with organic matter abundance,type,hydrocarbon generating capacity and shale oil potential due to the fact that higherδ^(15)N characterizes changes in the composition of the hydrocarbon generating bio-precursors.In the alkaline group withδ^(15)N>10‰,the organic matter types are good and shale oil potentials are higher,but the response relationship betweenδ^(15)N of source rocks and organic matter accumulation is not as good as that of the circum-neutral group,reflecting that the organic matter accumulation in alkaline group is influenced by other comprehensive factors other thanδ^(15)N.Accordingly,the organic matter accumulation models of three types of lacustrine source rocks(<5‰,5‰-10‰,and>10‰)classified on the basis ofδ^(15)N were established.Theδ^(15)N has the potential to trace organic matter accumulation and quality of source rocks.For example,lowδ^(15)N type(δ^(15) N<5‰)is of poor quality and medium-highδ^(15) N type(δ^(15) N>5‰)is of good qualityin lacustrine source rocks.This paper enriches the biogeochemical and hydrocarbon source rock geochemical studies of nitrogen by exploring organic matter accumulation in source rocks from the new perspective of nitrogen isotope composition and nitrogen cycling.
作者
曹剑
夏刘文
胡文瑄
Eva E STÜEKEN
支东明
唐勇
向宝力
何文军
CAO Jian;XIA Liuwen;HU Wenxuan;Eva E STÜEKEN;ZHI Dongming;TANG Yong;XIANG Baoli;HE Wenjun(School of Earth Science and Engineering,Nanjing University,Nanjing,Jiangsu 210023,China;School of Earth and Environmental Sciences,University of St Andrews,St Andrews,Scotland,KY169A,UK;PetroChina Tuha Oilfield Company,Hami,Xingjiang 839009,China;PetroChina Xinjiang Oilfield Company,Karamay,Xinjiang 834000,China)
出处
《石油实验地质》
CAS
CSCD
北大核心
2023年第5期912-925,共14页
Petroleum Geology & Experiment
基金
国家自然科学基金(42230808,42203055)
中国石油科技重大专项(2021DJ0108)联合资助。
关键词
有机质聚集
氮同位素
初级生产力
有机质保存条件
陆相烃源岩
organic matter accumulation
nitrogen isotopes
primary productivity
preservation conditions of organic matter
continental hydrocarbon source rocks
