Zhu Jieqiong, Deng Shuo, Wang Quan, Jiang Tao, Shi Yulei, Gao Ge, Hao Ziyan
PetroChina Huabei Oilfield Company, Renqiu 062552, China.
College of Geoscience, China University of Petroleum (Beijing), Beijing 102249, China.
ACS Omega. 2025 Aug 15;10(33):38002-38013. doi: 10.1021/acsomega.5c05212. eCollection 2025 Aug 26.
High-sulfur crude oils are widely developed in the saline lacustrine facies of the Jinxian Sag, yet their genetic mechanisms remain a subject of long-standing debate. Investigating these mechanisms is crucial for advancing petroleum genesis theories and guiding hydrocarbon exploration strategies. This study employs chromatography-mass spectrometry (GC-MS) in combination with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to analyze high-sulfur crude oil in the Jinxian Sag at the molecular level. The analysis identified heteroatom compounds, including NS, OS, OS, S, S, and S, with S class compounds being the predominant species. Organic sulfur compounds (OSCs) in crude oil have significant geochemical implications for assessing crude oil maturity. It is proposed that the ratios of DBE/DBE-S and C/C-DBE-S can serve as maturity indicators for crude oil. These parameters reflect the aromatization and side-chain cracking processes of OSCs during thermal evolution, providing a potential method for accurately delineating crude oil maturity and assessing highly mature oils. Unlike typical high-sulfur oils derived from thermochemical sulfate reduction, the studied samples lack a predominance of dibenzothiophenes (DBE-S). Instead, they are enriched in sulfur-containing compounds with biomarker-like carbon skeletons (C-DBE-S), which exhibit structural affinities to sterols formed via sulfate assimilation under the microbial reaction and subsequently incorporated into sediments. These compounds show a strong positive correlation with the sulfur content of the crude oils. In reducing environment, a large amount of inorganic sulfur undergoes intramolecular sulfurization with organic matter, primarily composed of sterol-like compounds, forming OSCs that retain the original carbon skeleton of the precursor compounds. These OSCs are subsequently incorporated into the kerogen, which is the primary mechanism for the formation of high-sulfur crude oil in the Jinxian Sag.
高硫原油在金县凹陷的盐湖相广泛发育，但其成因机制长期以来一直存在争议。研究这些机制对于推进石油成因理论和指导油气勘探策略至关重要。本研究采用色谱 - 质谱联用（GC - MS）结合傅里叶变换离子回旋共振质谱（FT - ICR MS）在分子水平上分析金县凹陷的高硫原油。分析鉴定出杂原子化合物，包括NS、OS、OS、S、S和S，其中S类化合物为主导物种。原油中的有机硫化合物（OSCs）对评估原油成熟度具有重要的地球化学意义。提出DBE/DBE - S和C/C - DBE - S的比值可作为原油成熟度指标。这些参数反映了OSCs在热演化过程中的芳构化和侧链裂解过程，为准确划分原油成熟度和评估高成熟油提供了一种潜在方法。与典型的源自热化学硫酸盐还原的高硫油不同，所研究的样品中缺乏二苯并噻吩（DBE - S）的优势。相反，它们富含具有生物标志物样碳骨架的含硫化合物（C - DBE - S），这些化合物在结构上与微生物反应下通过硫酸盐同化形成并随后纳入沉积物中的甾醇具有相似性。这些化合物与原油的硫含量呈现出强烈的正相关。在还原环境中，大量无机硫与主要由甾醇类化合物组成的有机物发生分子内硫化作用，形成保留前体化合物原始碳骨架的OSCs。这些OSCs随后被纳入干酪根，这是金县凹陷高硫原油形成的主要机制。
