原油成熟度FTIR光谱表征与盐度调控机制

doi:10.3964/j.issn.1000-0593(2025)11-3139-06

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摘要：为实现原油成熟度快速评价技术突破，创新性构建基于傅里叶变换红外光谱（FTIR）的原油成熟度判别模型。以济阳坳陷东营凹陷沙河街组三段、四段（Es₃、Es₄）烃源岩层系原油为研究对象，通过系统分析甾烷（C₂₉αββ/(ααα+αββ)、C₂₉20S/(20S+20R)）和萜烷（Ts/(Ts+Tm)）等生物标志物的成熟度参数，建立红外光谱特征与原油热演化程度的内在关联。通过基线校正、高斯-洛伦兹混合模型（Voigt函数）解卷积技术解析红外光谱特征，首次揭示脂肪烃振动区（2 800～3 000 cm^-1）特征峰面积比（A∑CH₂/A∑CH₃）与成熟度的关系：该比值从低熟阶段（C₂₉αββ/(ααα+αββ)=0.30）的4.33递减至高熟阶段（C₂₉αββ/(ααα+αββ)=0.60）的1.03。结合分子动力学分析发现，长链烷烃的β断裂作用是导致—CH₂—基团相对丰度随成熟度增加而降低的主要机制，其中低熟油中长链烷烃结构保存完整，而成熟油因热裂解作用产生显著的链烷烃短链化。在相同成熟度条件下，高盐环境（伽马蜡烷/C₃₀藿烷=0.81）原油的A∑CH₂/A∑CH₃值较淡水环境显著提升23.5%。分子模拟表明，盐度通过抑制硫化物裂解反应，有效延缓长链烷烃中—CH₂—基团的衰减过程，这为古盐度对有机质演化路径的影响提供了新的实验证据。相较于传统气相色谱-质谱（GC-MS）技术，本方法实现三大技术革新：（1）无损检测特性，仅需微量样品（<50 μL）即可完成分析，避免复杂前处理导致的样品损耗；（2）分析效率跃升，单样检测时间压缩至5 min内；（3）原位适用性突破，可直接应用于页岩油、致密油等非常规储层的原位成熟度评价，成功克服常规方法对可动烃含量的依赖。该研究成果为油气成藏动态分析提供分子尺度工具，并为页岩油等非常规资源评价开辟新技术路径，兼具理论创新与工程应用价值。

关键词：傅里叶红外光谱；成熟度；甲基与亚甲基基团；生物标志化合物

Abstract：To achieve breakthroughs in the rapid evaluation of crude oil maturity, this study innovatively established a maturity discrimination model based on Fourier Transform Infrared Spectroscopy (FTIR). The crude oil from the source rock series of Es₃ and Es₄ in the Dongying sag of the Jiyang depression is used as the research object. By analyzing the maturity parameters of biomarkers such as sterane (C₂₉αββ/(ααα+αββ), C₂₉20S/(20S+20R) ) and terpane (Ts/(Ts+Tm)), the intrinsic correlation between FTIR and thermal evolution degree of crude oil was established. In this study, Origin2025 software was used for baseline correction and Gaussian-Lorentz mixture model (Voigt function) deconvolution technology to analyze the infrared spectral characteristics. The relationship between the characteristic peak area ratio (A∑CH₂/A∑CH₃) of the aliphatic hydrocarbon vibration region (2 800～3 000 cm^-1) and maturity was revealed for the first time. The ratio decreases from 4. 33 in the low maturity stage (C₂₉αββ/(ααα+αββ)=0.30) to 1.03 in the high maturity stage (C₂₉αββ/(ααα+αββ)=0.60). Combined with molecular dynamics analysis, it is found that the β-cleavage of long-chain alkanes is the main mechanism for the decrease of the relative abundance of the —CH₂— group with the increase of maturity. The long-chain alkane structure in the low-mature oil is intact, while the mature oil produces significant short-chain alkane chaining due to thermal cracking. Under the same maturity conditions, the A∑CH₂/A∑CH₃ value of crude oil in a high-salinity environment ( gammacerane/ C₃₀ hopane=0.81) was significantly increased by 23.5% compared with that in a freshwater environment. Molecular simulation shows that salinity can effectively delay the decay process of the —CH₂— group in long-chain alkanes by inhibiting sulfide cracking reaction, which provides new experimental evidence for the influence of paleosalinity on the evolution path of organic matter. Compared to traditional gas chromatography-mass spectrometry (GC-MS) technology, this method achieves three major technological innovations. (1) Nondestructive testing characteristics. Only a small amount of sample (<50 μL) is required to complete the analysis, avoiding sample loss caused by complex pretreatment. (2) The analysis efficiency jumped, and the single-sample detection time was compressed to 5 minutes. (3) The breakthrough of in-situ applicability can be directly applied to in-situ maturity evaluation of unconventional reservoirs such as shale oil and tight oil, and successfully overcomes the dependence of conventional methods on movable hydrocarbon content. The research results provide a molecular-scale tool for evaluating unconventional resources, such as shale oil, which has both theoretical and engineering application value.

Key words：Fourier transform infrared spectroscopy; Maturity; Methyl (—CH₃) and methylene (—CH₂—) groups; Biomarker compounds

收稿日期: 2025-04-30 修订日期: 2025-08-20

中图分类号:

O657.3

基金资助: 国家自然科学基金项目(42073064，41473047)资助

作者简介: 张韩静，女，1992年生，中海油田服务股份有限公司综合地质工程师 e-mail: zhanghj82@cnooc.com.cn

引用本文:

张韩静，王飞，王涛，李敬松，李振，王娟，王金伟，郝鹏灵，李素梅，田苗，张宇，刘欢. 原油成熟度FTIR光谱表征与盐度调控机制[J]. 光谱学与光谱分析, 2025, 45(11): 3139-3144.
ZHANG Han-jing, WANG Fei, WANG Tao, LI Jing-song, LI Zhen, WANG Juan, WANG Jin-wei, HAO Peng-ling, LI Su-mei, TIAN Miao, ZHANG Yu, LIU Huan. FTIR Spectroscopic Characterization of Crude Oil Maturity and Salinity Regulatory Mechanisms. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2025, 45(11): 3139-3144.

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https://www.gpxygpfx.com/CN/10.3964/j.issn.1000-0593(2025)11-3139-06 或 https://www.gpxygpfx.com/CN/Y2025/V45/I11/3139