Nanoscale organic matter‐hosted pores (OM pores) are the dominant pore type in the marine, organic‐rich shales of the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation's first member in the Jiaoshiba Block, which provide important reservoir space for shale gas accumulation. In this study, field emission scanning electron microscopy (FE‐SEM), statistical analysis using ImageJ software, and gas adsorption tests were conducted to investigate the characteristics of OM pores, including pore shape, pore size distribution, pore quantity, and organic porosity. FE‐SEM images show that the OM pore sizes range between 2 and 900 nm. The predominant shape of the OM pores in the Wufeng shale is an irregular polygon, while elliptical and subrounded OM pores were observed in the Longmaxi Formation's first member shale. Average cross‐section area ratios of the OM pores to corresponding single‐particle organic matter (Ø_OMP/OM) for shale samples obtained via statistical analysis of FE‐SEM images range between 10% and 30%. We propose a new combination approach for the estimation of organic porosity, which gives organic porosities for the Wufeng shale and Longmaxi Formation's first member shale of 0.56%‐4.47% and 4.06%‐4.21%, respectively. To calculate the organic porosity for the OM pores with diameters of 10‐900 nm, the formula derived from the mass‐volume‐density‐organic matter relationships and Ø_OMP/OM of shale was used, while the organic porosity for pores with diameters of 0.3‐10 nm was estimated using carbon dioxide and nitrogen adsorption data. In addition, the reasons for the differences in the OM pore structures in the Wufeng shale and Longmaxi Formation's first member shale were examined for the study area and found to be the result of variations in total organic carbon (TOC) content and tectonic compression of the Wufeng shale.

中文翻译：

---

四川盆地焦石坝气田页岩有机质气孔结构特征及孔隙度估算

纳米级有机质孔隙（OM孔隙）是上奥陶统五峰组和志留系下龙马溪组的第一批成员在海洋上富含有机质的页岩中的主要孔隙类型，为页岩气提供了重要的储集空间积累。在这项研究中，进行了场发射扫描电子显微镜（FE-SEM），使用ImageJ软件的统计分析以及气体吸附测试，以研究OM孔的特征，包括孔的形状，孔径分布，孔数量和有机孔隙率。FE‐SEM图像显示OM孔径在2至900 nm之间。五峰页岩中OM孔的主要形状是不规则多边形，而在龙马溪组第一段页岩中观察到椭圆形和亚圆形的OM孔。通过FE‐SEM图像的统计分析获得的页岩样品的_{OMP / OM}范围在10％到30％之间。我们提出了一种新的组合方法来估算有机孔隙度，这使得五峰页岩和龙马溪组第一段页岩的有机孔隙度分别为0.56％-4.47％和4.06％-4.21％。要计算直径为10-900 nm的OM孔的有机孔隙率，可根据质量-体积-密度-有机物的关系和_{ØOMP / OM}得出公式使用的是页岩孔隙度，而使用二氧化碳和氮吸附数据估算了直径为0.3-10 nm的孔隙的有机孔隙度。此外，研究区域对五峰页岩和龙马溪组第一段页岩中的OM孔隙结构差异的原因进行了研究，发现其是总有机碳（TOC）含量变化和构造压缩的结果。五峰页岩。