中国海陆相页岩有机质孔隙发育特征对比——基于聚焦离子束氦离子显微镜（FIB－HIM）技术

为了明确不同成熟度的海陆相页岩有机质孔隙的发育特征，分别选取了中国中西部鄂尔多斯盆地的三叠系延长组陆相页岩、中国南方上扬子地区的下志留统龙马溪组以及下寒武统牛蹄塘组海相页岩等3组海陆相页岩样品，进行聚焦离子束氦离子显微镜（FIB-HIM）的观察实验。结果表明:延长组页岩样品的有机质孔隙发育数量较少，孔隙直径较小，有机质内部多发育微裂缝，页岩黏土矿物内部发育大量的粒间孔隙，粒内孔隙发育数量较少。龙马溪组页岩发育大量的有机质孔隙，大量较小直径的孔隙嵌套在直径较大的有机质孔隙中，增加了页岩孔隙的比表面积和孔隙连通性，有利于烃类气体在页岩有机质孔隙内的赋存及有效渗流。牛蹄塘组页岩内部发育数量最多的是粒间孔隙，有机质孔隙极少发育。有机质孔隙贡献了页岩孔隙系统的绝大部分有效赋存空间。页岩有机质孔隙的发育主要受控于热演化程度，过低的热演化程度（0.5% < R_o < 1.5%）无法形成大量的有机质孔隙及烃类气源供给；过高的热演化程度（3.0% < R_o < 4.0%）则会导致页岩有机质孔隙消失，烃类气体失去有效赋存场所而在地史过程中大量散失；适宜的热演化程度（1.5% < R_o < 3.0%）能够保证页岩有机质孔隙大量发育，有利于烃类气体在页岩储层中形成有效赋存和渗流。针对中国南方高—过成熟度海相页岩气的高效勘探开发，应寻找热演化程度适中的页岩层位。 

Comparison of organic matter pores of marine and continental facies shale in China: based on Focused Ion Beam Helium Ion Microscopy (FIB-HIM)

The continental shale in the Triassic Yanchang Formation in the Ordos Basin of the central and western China, and the marine shale in the Lower Silurian Longmaxi Formation and the Lower Cambrian Niutitang Formation in South China were chosen for Focused Ion Beam Helium Ion Microscope (FIB-HIM) observation in order to clarify the development characteristics of organic matter pores in marine and continental shale with different maturities. Few organic matter pores developed in the Yanchang shale, and the pore diameter is usually small. Micro-fractures are widespread in the organic matter, and a large amount of interparticle pores were present in the clay minerals of the shale. The Longmaxi shale samples developed a large number of organic matter pores, and there are many of small-diameter pores nested in large-diameter organic matter pores, which increased specific surface area and pore connectivity, and are favorable for the occurrence and migration of hydrocarbon gases in organic matter pores. The Niutitang shale samples contain a large number of interparticle pores and few organic matter pores. Organic matter pores contributed a vast majority of the effective storage space and connectivity of the pore system. The development of organic matter pores was mainly controlled by thermal evolution. Low thermal evolution (0.5% < R_o < 1.5%) can not forma large number of organic matter pores and hydrocarbon gas supply. Thermal evolution that is too high (3.0% < R_o < 4.0%) will lead to organic matter pore disappearance and hydrocarbon gas lost during geological history. The appropriate extent of thermal evolution (1.5% < R_o < 3.0%) ensures that organic matter pores are well developed, and is also important for the storage and seepage capacity for hydrocarbon gases in shale reservoirs. Therefore, for the exploration and development of highly-mature and over-mature marine shale gas in South China, the shale horizons with a moderate thermal evolution degree should be focused on.