泥页岩和煤中纳米孔隙的形成、演化和油气富集机制

This project will take the pore structural characteristics in shale and coal and the diagenetic evolution process as the main lines, study the formational and evolutional micromechanism of shale oil-gas and coalbed gas reservoirs from nanometer view. Through the overlapping and fusion of several subjects such as nano science and technology, geochemistry, coal geology and petroleum geology, a technique is explored to quantitatively detect the nanopores, scrutinize the pore structural characteristics of different shale and coal types under different geological conditions. Conbining with the thermal evolution simulation experiment and computer analog technology, this paper makes a profound analysis on the development characteristics, distribution patterns, controlling factors of the mud shale and coal and the influence on oil and gas enrichment. The network three dimensional structure model of different mud shales and coals is constructed. It reveals the origin of the nanopores, the diagenetic evolution process and the adsorption model of oil-gas in mud shale and coal, clarifies the relationship between the thermal evolution hydrocarbon-generating process and the formation of the nanopores in argillaceous source rocks. The impact of the evolution on oil-gas possibility is discussed. It offers new ways for basic research work to accurately describe and assess the reservior structure of mud shales and coals. It also provides important foundations for the formation and enrichment of shale oil-gas and coalbed gas.

本项目将以泥页岩和煤孔隙结构特征及成岩演化过程为主线，从纳米层次上研究页岩油气和煤层气储集空间形成和演化的微观机制。通过纳米科技、地球化学、煤地质学和石油地质学等多学科的交叉融合，探索一套纳米孔隙定量检测的技术方法，精细研究不同地质条件下不同类型泥页岩和煤的纳米孔隙结构特征，结合热演化模拟实验和计算机模拟技术，深入分析泥页岩和煤纳米孔隙的发育特征、分布模式、控制因素及对油气富集的影响，建立不同类型泥页岩和煤纳米孔隙网络三维结构模型，揭示泥页岩和煤纳米孔隙的成因、成岩演化过程及纳米孔隙对油气的吸附模式，阐明泥质烃源岩热演化生烃过程和纳米孔隙的形成关系，探讨纳米孔隙演化对泥页岩含油气性的影响，为泥页岩和煤储层结构精细描述和精确评价基础研究工作拓展新途径，也为页岩油气和煤层气的形成和富集提供重要的依据。

目前，非常规油气储层表征技术仍不完善，储集空间的发育机理存在诸多急需解决的难题，严重影响非常规油气的勘探和开发。本课题研究了不同技术方法表征非常规油气储层纳米孔隙的适应性以及不同沉积环境煤和泥页岩孔隙的特征、成因、控制因素、演化规律，探讨了页岩油储集空间的有效性。主要成果有：（1）研发了一种可有效表征非常规油气储层微纳米孔隙的新技术－低场核磁共振冻融法和八甲基环四硅氧烷联用技术，该技术可以完整地刻画非常规储层岩石4-1400nm的孔隙分布特征。（2）揭示了不同沉积环境页岩的孔隙特征和成因，探讨了不同沉积环境页岩纳米孔隙表征技术的适应性。海相、海陆过渡相、湖相泥页岩储层的非均质性呈现逐渐增大的特征；湖相页岩孔隙类型最为丰富，海相页岩的孔隙类型相对简单，海相高成熟度页岩有机质孔十分发育，湖相低成熟度页岩不发育有机质孔；多种技术方法可适用于高成熟度海相泥页岩的孔隙表征，而成熟度低、含油丰富的湖相页岩的表征以射线探测方法和核磁共振冻融法较为合适。（3）通过煤的热模拟实验，将煤次生孔隙的形成和演化分为三个阶段，早期壳质组生烃（Ro<1.5%），生成的孔隙主要来源于壳质组的解聚作用造成的体积收缩，形成的次生孔隙体积较大；第二阶段大致相当于Ro=1.5-2.0%，该阶段镜质组主要发生甲基化和缩聚作用，生成的孔隙为微米至纳米级；第三阶段相当于无烟煤阶段，该阶段主要是镜质组脱甲基作用和进一步的缩聚作用，主要形成纳米孔隙。（4）揭示了不同热演化阶段页岩介孔的演化特征及其控制因素。东营凹陷古近系沙三下亚段页岩细介孔体积百分比随热演化程度（埋深）增大呈现出先升高后降低的模式，粗介孔则显示相反的特征，Ro为0.7%是粗介孔与细介孔体积占比发生升降变化的拐点；粘土矿物含量与细介孔体积百分比呈正相关关系，与粗介孔体积百分比呈负相关关系。（5）基于抽提实验和负压实验，提出了5nm是东营凹陷页岩储层纳米孔隙储油的下限，10nm是页岩储层纳米孔隙中原油可流动的下限。