有机-无机协同作用对湖相泥页岩纹层间孔隙连通性的影响机制

The laminated shale is an important lithofacies type of lacustrine shale oil in China. Inter-lamina pore connectivity is one of the key factors that restricts the micro-short-distance migration and accumulation of shale oil, but less attention has been paid recently. This project conducts fine research on it by taking the lacustrine shale oil in the Permian Lucaogou Formation in the Santanghu Basin as an example, and by virtue of low field nuclear magnetic resonance - freezing and thawing - mercury intrusion measurement and other new pore structure characterization technologies for shale. Firstly, the experimental samples are optimized, and the microscopic observation of multi-functional thin sections and natural section samples is conducted to analyze the mineralogical and petrological characteristics organic matter-mineral symbiosis relationships of laminae; to divide basic lamina, layer combination, and thin layer type of laminae; and to identify the type and intensity features of diagenesis. Then, for the representative layer combination and thin layered laminae samples, a new method for the characterization of pore connectivity will be established, for revealing the difference of pore connectivity between different types of laminae; analyzing porosity types, morphology, micro-plane porosity, interface characteristics between laminae, and dissecting its internal association with inter-lamina pore connectivity. Finally, in combination with hydrocarbon - generating evolution of organic matter and oil - bearing properties of laminae, the organic-inorganic synergetic diagenesis evolution model for lacustrine laminated shale in the mature stage should be established, to further elucidate the influence mechanism of organic - inorganic synergistic effect on inter-lamina pore connectivity of lacustrine shale and to clarify its significance for the migration and accumulation of shale oil.

纹层状泥页岩是我国湖相页岩油发育的重要岩相类型，纹层间孔隙连通性是制约页岩油微-短距离运移聚集的重要因素，但前人关注较少。本项目以三塘湖盆地二叠系芦草沟组湖相页岩油为例，借助低场核磁共振-冻融-压汞联测等泥页岩孔隙结构表征新技术，开展精细研究。首先，优选实验样品，通过多功能薄片与样品断面镜下观测，分析纹层的矿物学、岩石学特征和有机质-矿物共生关系，划分基本纹层、层偶和纹层薄层种类，明确成岩作用类型与强度特征。然后，分别对典型层偶和薄层样品，建立孔隙连通性表征评价新方法，揭示不同类型纹层间孔隙连通性的差异；分析纹层孔隙类型、形态、微观面孔率和层间界面特征等，剖析其与纹层间孔隙连通性的内在关联。最后，结合有机质生烃演化和纹层含油性特征，建立生油演化阶段湖相纹层状泥页岩有机-无机协同成岩演化模型，进而阐明有机-无机协同作用对纹层间孔隙连通性的影响机制，并阐述其页岩油微观运聚意义。

本项目以三塘湖盆地二叠系芦草沟组湖相泥页岩为主要研究对象，通过泥页岩样品矿物学、岩石学和有机地球化学分析测试，以及大面积氩离子抛光、场发射扫描电镜观测、CT扫描、氮气吸附、多维核磁共振-高压压汞联测等系列实验，基于有机-无机共生关系与协同成岩演化，研究了泥页岩纹层间孔隙连通性及其影响机制，并阐明了对页岩油微-短距离运聚的意义。结果表明，湖相纹层状泥页岩物质来源多样，包含陆源碎屑物质、火山灰物质、碳酸盐等，从而造成纹层及其组合类型的多样性，如火山灰物质-碳酸盐、火山灰物质-粘土、碳酸盐-长英质/粘土等纹层组合。三塘湖盆地芦草沟组中凝灰岩、白云质凝灰岩、凝灰质白云岩、凝灰质泥岩等，纹层构造发育。孔隙类型包括粒间孔隙、脱玻化孔隙、溶蚀孔隙、白云石晶间孔隙、黄铁矿晶间孔隙、有机质孔隙，微裂缝包括纹层缝、成岩收缩缝、构造破裂缝等。纹层状泥页岩物质组成复杂多样，是孔隙类型多样化、孔隙结构复杂的重要原因。芦草沟组泥页岩纹层间孔隙的连通性较差，使富有机质纹层生成的液态烃向贫有机质纹层运聚受到限制，整体含油性降低。纹层间伴生的层间微裂缝是页岩油富集和渗流的主要介质。纹层间孔隙的连通性主要受纹层矿物组成和有机-无机协同成岩作用影响。芦草沟组泥页岩正处于生油窗范围，有机质孔隙的发育受到限制。黄铁矿、火山灰物质的催化生烃作用，可在一定程度上促进有机质的成烃转化，有利于有机质孔隙的发育，进而有利于干酪根-有机质孔隙-无机矿物孔隙-微裂缝形成有效的微观源储沟通系统。这是影响富有机质纹层与无机矿物纹层间孔隙连通性及其含油性的重要机制。泥页岩中微观裂缝的发育情况及其与微孔隙的有效配置，对纹层状泥页岩液态烃富集有着重要作用。