Insights into Characterizing Pore Structures in Marine Shale of the Ordos Basin by LNG and SEM

Shale gas has had a significant impact on the global energy landscape. Recently, attention has shifted towards the marine shale of the Ordovician Wulalike Formation in the Ordos Basin, which differs significantly from the shale in the Longmaxi Formation in the Sichuan Basin due to variations in sedimentary environment. As the pore structure of shale strongly influences the storage and transport of shale gas, accurately characterizing the pore structure of the Ordos Basin shale is critical. In this study, low temperature nitrogen adsorption (LNG) and scanning electron microscopy (SEM) were employed to investigate the pore structure of the Ordos Basin shale. The results indicate that the Wulalike shale has two prominent peaks at 9.48 nm and 21.8 nm, suggesting a large number of nanopores in the 10–20 nm range. Based on the analysis, the marine shale is primarily composed of mesopores (2–50 nm) at 80.08%, followed by macropores (>50 nm) at 19.59% and micropores (<2 nm) at 0.34%. Furthermore, the Wulalike shale contains organic pores, intragranular pores, intergranular pores, and cracks, with pores dispersed and independent of one another. The pore morphology is diverse, but with an overall appearance of fissure-like pores. This study provides crucial insights into the pore structure of the shale in the Ordos Basin.