烷基萘分子稳定碳同位素组成演变的热模拟实验及其意义  

Stable carbon isotopic dynamics of alkylated naphthalenes accompanying thermal maturation: Implications for oil/oil, oil/source correlation

作　　者：蒋爱珠[1,2] 谢柳娟[3] 张永东[1,2] 柴平霞[1] 孙永革[1,3] 王飞宇 

机构地区：[1]中国科学院广州地球化学研究所有机地球化学国家重点实验室,广东广州510640 [2]中国科学院大学,北京100049 [3]浙江大学地球科学系,浙江杭州310027 [4]中国石油大学地球科学系,北京102200

出　　处：《地球化学》2013年第6期509-522,共14页Geochimica

基　　金：国家自然科学基金(40972093;41172112)

摘　　要：萘及烷基萘是原油和沉积有机质的重要组成。目前对于烷基萘单体稳定碳同位素组成随有机质成熟作用加深的演变特征鲜见报道。本研究选取松辽盆地杜601井嫩一段低熟黑色泥岩进行热压模拟生烃实验,采用两步柱色谱层析技术分离烷基萘化合物使其达到稳定碳同位素的在线准确测定,从而厘定有机质不同成熟阶段烷基萘单体稳定碳同位素组成分布面貌。实验结果显示,不同模拟实验温度点排出的一甲基萘(MNs)和二甲基萘(DMNs)各异构体具有相对一致的稳定碳同位素值,分别介于–29.5‰~–29.3‰和–30.9‰~–30.5‰之间,这可能与生烃过程中干酪根的非均一性裂解有关;三甲基萘(TMNs)各异构体之间稳定碳同位素值差异较大,介于–36.8‰~–31.1‰之间,这可能与生源效应有关;其中,1,2,5-TMN稳定碳同位素组成偏轻,介于–36.8‰~–35.6‰之间,可能是细菌来源的藿类化合物降解及其芳构化的产物。实验结果表明,随着有机质热演化作用的加深,烷基萘单体稳定碳同位素组成变化介于0.8‰~1.4‰之间,基本在仪器测试误差范围之内,反映成熟作用所导致的烷基萘单体稳定碳同位素动力学分馏较小。因此,烷基萘单体稳定碳同位素组成可以成为油-源和油-油对比的潜在指标。Naphthalene and methylated naphthalenes organic matter. But there are few reports about the are common constituents of petroleum and sedimentary characteristics of stable carbon isotopic composition of methylated naphthalenes accompanying thermal maturation. In this work, an immature black shale from the Du601 well in the Songliao Basin, northeast China, is employed to the simulation of hydrocarbon generation under semi-closed pyrolysis system. Alkylated naphthalenes in pyrolysates are separated and enriched to meet the demand for on-line determination of stable carbon isotope by using the two-step column chromatography. The variations in stable carbon isotopic compositions of individual methylated naphthalenes with maturity are investigated by compound-specific isotope analysis of oils expelled at progressive pyrolysis temperatures. The results show that similar t^13C values occur within both methylnaphthalenes （MNs） isomers and dimethylnaphthalenes （DMNs） isomers, their fi13C values being in the range of-29.5‰--29.3‰ and -30.9‰--30.5‰, respectively. It might be related to the nonspecific cracking of kerogen during the hydrocarbon generation. In addition, a large difference is observed between trimethylnaphthalenes （TMNs） isomers, varying from-36.8‰ to-31.1‰, which is attributed to source effect. The 013C value of 1,2,5-TMN in TMN isomers is most negative, falling between-36.8‰ and-35.6‰, suggesting that it is products of hopanoids derived from bacteria via degradation and aromatisation. The stable carbon isotopic fractionation of individual methylated naphthalenes caused by thermal maturation is between 0.8‰ and 1.4‰. As the δ13C values of individual mathylated naphthalenes are mainly controlled by source effect and hardly affected by maturity, the stable carbon isotopic curve of methylated naphthalenes is an effective implication of oil/source, oil/oil correlation.

关 键 词：烷基萘 分子碳同位素 有机质成熟作用 油-源对比 油-油对比 

分 类 号：P593[天文地球—地球化学]