## 4 Results
### Pore Type and Morphological Characteristics  
Shale pores are the storage space for gas in shale gas reservoirs, and the microscopic characteristics of the pores largely determine the performance of the shale reservoir [45; 46]. According to the genetic mechanism, morphological characteristics, and development location of pores, shale pores can be classified into three categories: inorganic pores, organic pores, and microfractures. Among them, inorganic pores mainly include mineral InterP and IntraP pores [47; 48]. The results of SEM show that various pore types develop in the shale samples of the Taiyuan Formation in the SNCB, mainly including organic pores, mineral InterP pores, IntraP pores, and microfractures (Figures 7 and 8).  
Organic pores are secondary pores formed during the thermal evolution stage when kerogen is converted into hydrocarbon fluids, primarily developing inside and between organic particles. The organic matter contains nanoscale pores and microfractures, which are small in size and not connected (Figure 7a,b). Some organic matter can fill the InterP pores of strawberry pyrite (Figure 7d), interlayer pores of clay minerals (Figure 7b), and  
Figure 7: The development characteristics of organic pores in the Taiyuan Formation shale in the SNCB. (**a**) Organic matter shrinkage joints and organic pores; (**b**) InterP pores, organic pores and organic matter shrinkage joints; (**c**) InterP pores and organic matter shrinkage joints; (**d**) Organic matter and pyrite.  
calcite crystals (Figure 8d), forming organic-mineral complexes. The organic matter in these complexes hardly developed internal pores, and some organic matter particles did not develop internal pores (Figure 7c,d).  
Some InterP pores are often developed at the edges of mineral particles in the Taiyuan Formation shale (Figure 8). The pore morphology, mostly triangular, banded, or irregular, is controlled by the original pores and diagenesis compaction, and the pore connectivity is good. A small number of IntraP pores develop in the brittle mineral particles (Figure 8a,d). Due to their small pore size and poor connectivity, they have little effect on the enrichment and migration of shale gas. The carbonate unstable minerals develop a small number of dissolution pores due to the influence of acidic fluids (Figure 8b), and these dissolution pores are mostly isolated from each other. The formation of dissolution pores in the gas window has a positive impact on the occurrence of shale gas. Microfractures with various shapes can also be observed in shale samples, primarily shrinkage fractures between clay mineral layers. During the diagenetic process of clay minerals, smectite undergoes a transformation from I/S mixed layer to illite. This transformation is accompanied by dehydration and volume reduction, resulting in shrinkage fractures between clay mineral  
Figure 8: The development characteristics of mineral pores in the Taiyuan Formation shale in the SNCB. (**a**) InterP pores and IntraP pores; (**b**) InterP pores and IntraP pores; (**c**) InterP pores and organic matter; (**d**) InterP pores, IntraP pores, organic matter and calcite.  
layers. Additionally, the pore connectivity is good. However, under intense compaction, clay mineral particles are arranged more closely, leading to deformation and closure of pores between them (Figure 8c).