页岩油赋存及运移孔径下限的纳米多孔材料模拟研究

The United States achieved "shale gas revolution", which has changed the Global energy pattern, and shale oil is likely to become the future "revolutionary" of unconventional oil resources. The nano-characterization techniques achieved key breakthroughs in the shale gas reservoir related research, and " Nano oil & gas" in shale tiny pores also attracted more attention. The theory of “Nano oil & gas” is constantly breaking through the pore throat threshold of reservoirs. The existence of the lower threshold of the pore size has important strategic research value. The lower threshold of the pore size determines the statistical calculation of the effective porosity of shale oil reservoirs, and then determines the total amount of geological resources in the evaluation of tight oil. In order to solve this scientific problem, understanding the physical and chemical properties of oil shale is the basic scientific premise. First of all, the physical structure and chemical characteristics of natural shale should be accurately characterized, and its behaviors of transportation, storage status, and wettability of oil in pore throats also need to be understood. Such pre-requisition is essential for the exploration of shale oil, while however, taking shale for example, the ultra-small spaces of the pores and complexities of the chemical surroundings hinder the progress of researches. In order to solve such problems, this project intends to use chemically modified nano-porous templates with uniform and controllable channel size to simulate natural shale pores, then by combining micro numerical simulation to find out the lower limit of oil occurrence and free access under certain temperature-pressure condition. This project is about to find out the lower threshold of the pore size which forbids the entering of oil and water, as well as the occurrence and free access regular pattern of oil in the micro and nano pore throats. The conclusion of this research is believed to be helpful in the calculation of the potential reserves of shale oil.

美国实现“页岩气革命”，正改变全球能源格局，而页岩油可能成为未来非常规石油资源“革命者”。在页岩气储层研究中，纳米表征技术使赋存在微小孔隙的“纳米油气”登上舞台。“纳米油气”理论正不断突破石油储集最小孔喉极限，“是否存在储集下限?”这个问题具有重要研究价值。孔隙储集下限决定页岩油储层有效孔隙的计算，左右页岩油地质资源总量评价。为解决这个科学问题，亟需开展页岩油储层理化特性、在微纳米孔喉中赋存状态、储集能力以及润湿性等方面的研究。而作为页岩油主体储集空间的纳米级孔喉空间狭小、结构复杂、非均质性强，给研究带来困难。为此，本项目将制备系列具有均一直径的纳米管道多孔材料，通过化学修饰使其接近原油在天然页岩储层的界面自由能，在一定温压条件下逐一研究油在不同孔径孔隙中的赋存状态和运移能力，结合微观数值模拟验证，探究页岩油地层条件下聚集和自由进出的下限阈值，为页岩油资源量计算和未来高效开采提供理论参考。

页岩油是中国陆上最具发展潜力的战略性接替资源，也是我国应对油气对外依存度日益攀升的必然选择，但富有机质页岩强非均质性为储层有效性评价、流体分布预测、资源量计算和高效开发带来难题。课题负责人一直从事纳米油气多学科交叉创新研究，聚焦页岩油勘探开发基础科学问题，突破储层非均质性和有效性定量评价以及赋存与运移综合模拟领域技术瓶颈，针对页岩油藏的储集空间（孔喉、裂缝）、岩石结构（矿物、有机质）、流体特征3方面，建立了复杂储层多尺度数字岩石评价技术及工作流程，系统揭示页岩油微纳孔喉系统的科学意义和工业价值。储集空间评价方面：二维大面积分析技术可建立跨越7个数量级的多尺度选取及非均质性评价；多尺度CT及FIB-SEM联用可精确刻画孔喉和裂缝的三维空间分布；采用电沉积法将金属填充在岩石薄片的连通孔隙中，然后对岩石部分进行选择性溶解，得到孔喉结构复形的金属结构物，利用扫描电子显微镜对金属的结构和形貌进行表征，从而直接观察到小于50nm、大范围的页岩三维微观结构，并计算页岩连通孔隙和喉道的表面积。固体组分分析方面：XRF及QEMSCAN联用可定量评价矿物组成与分布；三维FIB-SEM技术可以实现有机质形态和分布的定量分析。流体特性方面：通过合成孔径、润湿性、表面微结构均可调控的纳米材料，开展地层条件下页岩油赋存及流动物理模拟研究，确定了单一因素对页岩油赋存及可动孔径下限的影响，明确页岩油赋存孔径下限为20nm，可自由进出下限为200nm，突破了经典油气储层理论孔喉下限；利用分子模拟研究油气在无机、有机质纳米孔隙中的聚集机理与扩散潜力。最后，利用多尺度数字岩石评价技术体系对中美页岩油储层微观特征进行了对比研究，为中国陆相页岩油有利区和开发方式优选提供技术支撑。