湖相未熟-低熟页岩油形成与聚集机理

Shale oil has become one of the most important unconventional petroleum resources around the world. Lacustrine immature to low mature organic-rich shales are widely distributed in China. The potential of lacustrine immature to low mature shale oil resources is undefined. Formation and accumulation mechanisms of immature to low mature shale oil are the key scientific problems to be studied. The immature to low mature organic-rich shale in the second section of Kongdian formation in Cangdong Sag, Huanghua Depression, Bohai Bay Basin will be studied as research object in this project. Synthetic methods combining geological and geophysical-geochemical inversion method with simulation experiment forward method will be used. The organic and inorganic petrology and its heterogeneity will be discussed. Qualitative and absolute quantitative indicators of biomarker are going to be adopted in oil-rock correlation analysis. Hydrocarbon generation thermal simulations of whole rock, soluble organic matter and kerogen will find out the hydrocarbon generation potential and the formation mechanism of immature to low mature shale oil. High precision testing analysis including nano-CT and hydrocarbon generation-retained accumulation simulation experiments will be integrated to describe the micro-nano pore space and structure delicately and understand the development and evolution mechanism and influence factors of micro-nano reservoir space. The shale oil accumulation mechanism during the diagenesis and hydrocarbon generation of immature to low mature shale will be revealed. This study will provide scientific foundation for resource evaluation and exploration and development of immature to low mature shale oil.

页岩油已成为全球重要的非常规油气资源之一。中国湖相未熟-低熟富有机质页岩分布广，蕴含的页岩油资源潜力不明，未熟-低熟页岩油形成和聚集机理是亟待研究的关键科学问题。本项目以渤海湾盆地黄骅坳陷沧东凹陷孔二段未熟-低熟富有机质页岩为研究对象，采用地质-地球物理-地球化学反演与模拟实验正演相结合的方法，研究未熟-低熟富有机质页岩的岩石矿物学、有机岩石学特征及其非均质性；利用生物标志物定性和绝对定量指标开展油-岩对比；对全岩、可溶有机质以及干酪根分别开展生烃热模拟实验，探讨未熟-低熟页岩生烃潜力和页岩油形成机理；将纳米CT等高精度分析测试与生烃-滞留聚集模拟实验相结合，精细刻画未熟-低熟页岩微米-纳米级孔隙类型与孔隙结构，研究微米-纳米储集空间的发育演化机制与影响因素，深入认识未熟-低熟富有机质页岩成岩及生烃过程中的页岩油聚集机理，为未熟-低熟页岩油资源潜力评价和勘探开发提供科学依据。

中国湖相盆地中广泛发育未熟-低熟页岩，页岩油资源潜力不明，其形成和聚集机理亟待研究。本项目以渤海湾盆地沧东凹陷孔二段未熟-低熟富有机质页岩为研究对象，综合运用地质、地球物理及地球化学方法，系统研究了湖相未熟-低熟富有机质页岩的岩石矿物学特征、地球化学特征及其非均质性分布、储集空间发育演化、未熟-低熟页岩油地球化学特征、含油性表征及热演化过程中的页岩油形成聚集机理。研究表明，沧东凹陷孔二段湖相未熟-低熟页岩层系岩石及矿物组成非均质性强，发育多种类型岩相，层序地层格架控制了岩相的非均质性分布。提出了利用声波时差-自然伽马重叠技术对湖相页岩层系岩性进行快速识别的方法并建立了岩性识别图版，构建了一套以矿物组分、构造类型为划分依据的岩相分类方案。未熟-低熟页岩主要分布于湖盆中央半深湖-深湖相发育区，有机质丰度高且分布明显受沉积微相的控制，平面上呈环带状分布，有机质类型以Ⅱ型和Ⅰ型为主。不同类型岩相的有机质类型和生烃潜力存在差异，云质页岩、混合质页岩、砂质页岩和泥质页岩为中—高有机碳岩相，对油气生成和有机质孔发育最有利。未熟-低熟页岩发育有基质孔隙和裂缝两类储集空间，晶间孔、颗粒间孔、粘土矿物片间孔及有机质孔是最主要的孔隙类型，不同类型岩相孔隙发育及孔隙结构存在差异，微孔和中孔是页岩油的主要储集空间。探索了地球化学指标法、核磁共振实验法、测井评价法等多种方法定量表征页岩含油性。自然演化剖面和生烃-滞留聚集模拟实验分析表明，在未熟—低熟生烃演化阶段，孔隙以原生孔隙为主，有机质孔等次生孔隙欠发育，成熟生烃演化阶段有机质孔、溶蚀孔、微裂缝等次生孔隙大量发育，平均孔径大幅度减小，比表面积和总孔体积则大幅增加，Ro在0.9%~1.5%之间页岩含油性最好。项目研究成果为进一步评价湖相未熟-低熟页岩油资源潜力奠定了基础。