石油与天然气地质 ›› 2023, Vol. 44 ›› Issue (1): 150-163.doi: 10.11743/ogg20230112

• 油气地质 • 上一篇    下一篇

原油热裂解过程中的红外光谱演化特征及其主控因素

刘博通1,2,3(), 程鹏1,2(), 盖海峰1,2, 周秦1,2, 李腾飞1,2, 田辉1,2   

  1. 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 深地科学卓越创新中心, 广东 广州 510640
    3.中国科学院大学, 北京 100049
  • 收稿日期:2022-06-01 修回日期:2022-11-18 出版日期:2023-01-14 发布日期:2023-01-13
  • 通讯作者: 程鹏 E-mail:liubotong19@mails.ucas.ac.cn;chengp@gig.ac.cn
  • 第一作者简介:刘博通(1997—),男,硕士研究生,油气地球化学。E-mail:liubotong19@mails.ucas.ac.cn
  • 基金项目:
    国家重点研发计划项目(2019YFC0605502);国家自然科学基金项目(42272162);中国科学院A类战略性先导科技专项(XDA14010104);广东省自然科学基金项目(2021A1515011381)

Infrared spectra evolution of crude oil under pyrolysis and its controlling factors

Botong LIU1,2,3(), Peng CHENG1,2(), Haifeng GAI1,2, Qin ZHOU1,2, Tengfei LI1,2, Hui TIAN1,2   

  1. 1.State Key Laboratory of Organic Geochemistry,Guangzhou Institute of Geochemistry,CAS,Guangzhou,Guangdong 510640,China
    2.Center for Excellence in Deep Earth Science,CAS,Guangzhou,Guangdong 510640,China
    3.University of Chinese Academy of Science,Beijing 100049,China
  • Received:2022-06-01 Revised:2022-11-18 Online:2023-01-14 Published:2023-01-13
  • Contact: Peng CHENG E-mail:liubotong19@mails.ucas.ac.cn;chengp@gig.ac.cn

摘要:

原油的红外光谱能够反映原油中各种分子基团的信息,对于简单、快速识别原油的成因类型和热演化程度有很大的应用潜力。通过对两个不同有机相来源的原油样品开展热解实验,初步研究了原油热解过程中红外光谱的演化特征及其主控因素。结果表明,随着原油热解程度的增加,不同类型原油的红外光谱具有相似的演化模式,可近似划分为两个阶段。在早期阶段(实验温度< 370 ℃),热解油中甲基/亚甲基吸光度比值(ACH3/ACH2)变化不明显,而芳环分子基团吸光度(Aaro)及其与烷基分子基团吸光度比值(Aaro / Asat)减小,这主要是由于原油中部分热稳定性低的化合物发生脱支链作用,形成了饱和烃组分,降低了芳烃/饱和烃比值。在晚期阶段(实验温度> 370 ℃),热解油中ACH3/ACH2AaroAaro /Asat 均显著增大,这主要是由于化合物中长分子链结构断裂,形成富含短分子链结构的化合物,造成甲基分子基团的含量增加;同时,热解油中化合物的芳构化程度显著增加,造成芳烃含量和芳烃/饱和烃比值增大。在原油热解过程中,不同类型原油的红外光谱参数存在一定的差异性,尤其是处于原油热解的早期阶段。因此,原油的红外光谱参数图版可以应用于划分原油类型和识别原油的热演化程度。

关键词: 热解程度, 红外光谱, 芳烃含量, 饱和烃含量, 热解实验, 原油

Abstract:

Infrared spectra of crude oils can indicate information of various molecular groups, which is of great potential to identifying the genetic type and thermal evolution degree of crude oil. In this study, pyrolysis experiments are performed on two immature crude oil samples from different organic facies, to preliminarily investigate the infrared spectra evolution of crude oils under pyrolysis and its controlling factors. The results indicate that the infrared spectra evolutions are similar for the two oil samples and can be approximately divided into two stages with the increase in oil cracking extent. At the early stage with experiment temperatures of lower than 370 ℃, the ACH3/ACH2 value of cracking oil varies slightly, while the Aaro and Aaro/Asat values progressively decrease. This is due to some compounds with a weak thermal stability undergoing debranching during this stage, which results in an increase in saturated hydrocarbon content and decrease in the ratio of aromatic/saturated hydrocarbons. At the later stage with experiment temperatures of over 370 ℃, the ACH3/ACH2Aaro and Aaro/Asat values of oil samples significantly increase mainly due to the compounds with long molecular chain structures significantly cracked into compounds with short molecular chain structures, causing an increase in the ACH3 content. Meanwhile, the aromatization degree of the compounds is significantly enhanced at this stage, which results in an increase in aromatic hydrocarbon content as well as the ratio of aromatic/saturated hydrocarbons. There are still some differences in the infrared spectral parameters between the two oil samples during the oil cracking process, especially at the early stage. Therefore, cross plots of infrared spectral parameters, such as the plot of ACH3/ACH2-Aaro/Asat, can be used to classify the types of crude oils and identify their thermal maturity.

Key words: extent of thermal cracking, infrared spectra, content of aromatics, content of saturates, pyrolysis experiment, crude oil

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