Abstract Understanding the differences among shale pore systems is crucial to exploring the enrichment mechanism of shale gas. In this study, we found that radiolarian micro-fossils are widely distributed in the overmature marine organic-rich Wufeng-Lungmachi formations surrounding the Sichuan Basin, South China. This enables an investigation on the full-scale pore structure characteristics of the two formations by using a combination of qualitative methods (field emission scanning electron microscopy (FE-SEM)) and quantitative methods (low-pressure N2 and CO2 adsorption and high-pressure mercury intrusion porosimetry (MIP)). The results show that micropores (accounting for 75.81%) and mesopores (accounting for 63.56%) are mainly responsible for the total surface area and the total pore volume, respectively. Furthermore, organic matter significantly contributes to the shale surface area, and the intercrystalline pores of clay minerals make an important contribution to the pore volume of shale. Abundant biological pores can be discovered in radiolarian fossils, and these biological pores belong to mesopores and macropores. The investigation of gas adsorption shows that radiolarian-poor shale reflects the presence of slit-shaped pores, while radiolarian-rich shale indicates the presence of ink-bottle-shaped pores. In addition, despite similar TOC contents, clay minerals and brittle minerals, radiolarian-rich layers have larger pore volumes than radiolarian-poor layers. The results calculated using the threshold method with ImageJ software show that the average surface porosities of the organic matter, mineral matrix, and radiolarians are 15.69%, 1.84%, and 5.34%, respectively. Given that the quantitative calculation results in a greater contribution by the pores developed in radiolarians, the biological pores developed in radiolarians are beneficial for the enrichment of free gas.

中文翻译：

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放射虫化石对四川盆地五峰—龙马池气页岩（奥陶系—志留系）孔隙结构影响的量化

摘要 了解页岩孔隙系统之间的差异对于探索页岩气富集机制至关重要。在这项研究中，我们发现放射虫微化石广泛分布在华南四川盆地周围的过成熟海洋富含有机物五峰-龙马池地层中。这使得通过使用定性方法（场发射扫描电子显微镜 (FE-SEM)）和定量方法（低压 N2 和 CO2 吸附以及高压压汞法（MIP））。结果表明，微孔（占75.81%）和中孔（占63.56%）分别是总表面积和总孔容的主要来源。此外，有机质对页岩表面积贡献显着，粘土矿物晶间孔对页岩孔隙体积贡献重要。在放射虫化石中可以发现丰富的生物孔，这些生物孔属于中孔和大孔。气体吸附研究表明，贫放射虫页岩反映了狭缝状孔隙的存在，而富放射虫页岩则表明存在墨瓶状孔隙。此外，尽管 TOC 含量、粘土矿物和脆性矿物相似，但富含放射虫的层比贫放射虫的层具有更大的孔隙体积。ImageJ软件阈值法计算结果表明，有机质、矿物基质和放射虫的平均表面孔隙度分别为15.69%、1.84%和5.34%，分别。鉴于定量计算结果表明放射虫发育的孔隙贡献更大，因此放射虫发育的生物孔隙有利于游离气的富集。