## 2 Analysis of Micro-Structure Features of the Shale Gas Reservoir  
The study area encompasses the Longmaxi Formation in the Fuling region, focusing on the shale gas reservoir within this exploration interval. This reservoir consists of black organic-rich shale formed under prolonged exposure to reducing conditions. The sedimentary environment is characterized by deep- to shallow-water shelf deposition. The structural features of surrounding faults in the Fuling area create favorable conditions for shale gas preservation. However, the shale gas reservoirs in this region exhibit intricate microstructural characteristics and mineral compositions, presenting challenges for geophysical exploration and quantitative characterization. Therefore, conducting geological studies and employing effective RPMs for accurate reservoir simulation are imperative. Subsequently, quantitative seismic rock physics studies are necessary for a comprehensive understanding.  
Through the analysis of mineral composition, scanning electron microscope (SEM) figures, and structural figures of the shale gas reservoir, a high-precision seismic RPM can be developed. This model will serve as the foundation for subsequent quantitative seismic characterization using pre-stack seismic inversion data.  
The lithology of the target interval is primarily characterized by black carbonaceous shale, displaying low velocity, low density, and low porosity features. As illustrated in Figure 1, well log mineral composition data from the study area reveal quartz and clay as the predominant minerals in the target interval. Additionally, minor amounts of calcite and dolomite are present. The rock physics modeling process must account for these complex mineral compositions.  
Figure 2 presents SEM images of shale gas reservoirs [28]. In Figure 2a, a well-defined horizontal bedding structure with distinct alternating patterns is evident in the reservoir. Figure 2b unveils the inorganic pore structure, featuring intergranular pores formed by irregular debris particles, exhibiting pore shapes ranging from slit-like to wedge-shaped.  
Figure 1: Well log data of mineral types and contents in shale.  
Figure 2c showcases the organic pore structure, indicating substantial organic matter development in the shale gas reservoir. The organic matter presents numerous pores with a honeycomb or banded shape, demonstrating varying sizes and a certain degree of connectivity.  
Figure 3 displays structural figures of the target well in the study area. In Figure 3a, a rose diagram reveals a relatively stable orientation, predominantly trending towards the southwest. The histogram analysis depicted in Figure 3b indicates that the dip angles of the strata primarily fall within the range of 0\({}^{\circ}\) to 30\({}^{\circ}\).  
The pores within shale reservoirs play a pivotal role as primary storage spaces and migration pathways for oil and gas. However, the inherent limitations of well log tools, with high vertical but limited lateral resolution, hinder the direct measurement of microphysical characteristics, structural intricacies of reservoirs, and seismic anisotropy parameters. Hence, establishing a rock physics model (RPM) for the target reservoir becomes imperative. This RPM aids in calculating the impact of complex mineral composition, pore shapes, pore connectivity, and other microstructures on the seismic anisotropy of the reservoir. Additionally, there is a need to explore quantitative characterization methods for both reservoir physical parameters and anisotropy parameters.  
Figure 3: Well structural figures: (**a**) Rose diagram of azimuths; (**b**) Histogram of formation dip angles.  
Figure 2: SEM images of the sampled cores showing microstructures of the shale: (**a**) Horizontal bedding structure; (**b**) Inorganic pore structure; (**c**) Organic pore structure.