沥青质大分子的结构及其测定方法综述

Review on molecular structures of asphaltene macromolecules and instrumental analytical approaches

沥青质是石油或岩石可溶有机质的重要组分之一,通常具有复杂的大分子结构和较高的分子量。沥青质中包裹(或键合)的生物标志物被认为具有重要的油气地球化学研究价值,而对沥青质大分子的实际分子量和分子结构的研究在油藏勘探开发、地球化学实验以及油品存储、运输和炼化生产等方面也具有潜在价值。对文献中报道的沥青质结构、分子量及相关的实验测定方法等开展综述,试图为沥青质的分子结构、分子量以及物理化学性质提供更加全面的认识,从而为沥青质地球化学研究在常规、非常规油藏勘探、开发研究中的应用提供基础资料。针对沥青质分子的结构及分子量方面存在的不同观点开展成果综述并结合实验测定技术的现状探讨了存在争议的主要原因,指出相关研究的下一步发展方向。目前对沥青质大分子结构的认识主要是基于两种完全不同的模型,即“孤岛”模型和“群岛”模型。前者认为沥青质具有单个芳核,表征的分子量相对较低;而后者则认为沥青质具有多个芳核,表征的分子量高。上述两种沥青质分子结构的模型均有各自的实验测定结果得以支持,其中“孤岛”模型的证据主要来自荧光光谱及激光气化/离子化质谱(L2MS)分析以及基于不同离子化方式的高分辨质谱(FT-ICR-MS)分析技术;“群岛”模型的证据主要来自气相渗透测量法、体积排阻色谱法和化学降解法等。

As one of the major fractions of petroleum and/or source rock extracts,asphaltene is commonly characte-rized by complicate molecular structures as well as relatively higher molecular weight(MW).The asphaltene occluded biomarkers have been well introduced to be valuable for geochemical research whilst the actual molecular weight and molecular structures of asphaltene macromolecules studies show value in petroleum exploration and production,labora-tory treatments as well as petroleum chemical storage and transportation etc.The structure,molecular weight and related experimental measurement methods of asphaltenes reported in this paper are reviewed,in an attempt to provide a more comprehensive understanding on the molecular structure,molecular weight and physicochemical properties of asphaltenes,so as to provide basic data for applying asphaltene geochemical research in the exploration and develop-ment study of conventional and unconventional reservoirs.In view of the different views on the structure and molecular weight of asphaltene molecules,the results are reviewed,the main reasons for the controversy are discussed based on the current status of experimental measurement technology,and the future development trend of related researches is pointed out.The current understanding of the structure of asphaltene macromolecules is mainly based on two completely different models,i.e.,the island model and archipelago model.The former suggests that asphaltenes have a single aromatic nucleus and the molecular weight characterized is relatively lower.The latter believes that asphaltenes have multiple aromatic nuclei and the molecular weight characterized is relatively higher.The above two models of asphaltene molecular structure are supported by their own experimental measurement results,among which the evidences of the“island”model mainly come from fluorescence spectroscopy,laser vaporization/laser ionization mass spectrometry(L2MS)analysis and stem from various ionization high-resolution(Fourier transform ion cyclotron resonance mass spectrometry,FT-ICR-MS)analysis technologies.The evidences for the archipelago model mainly come from gas phase permeation measurement,size exclusion chromatography and chemical degradation.