## 6 The Impact of Low-Resistivity Shale Reservoir Characteristics on Gas-Bearing Properties
Currently, it is widely recognized that water saturation significantly affects adsorption capacity, with dry shale showing notably greater adsorption than its hydrated counterpart. Once water saturation reaches a certain threshold, the effect lessens [29]. Extensive research suggests that at 40% water saturation, shale's adsorbed gas volume drops to 30% of dry shale. As water saturation rises, the variation in adsorbed gas volume becomes minimal. In normal resistivity shale gas wells, the water saturation in the shale reservoir stands at approximately 20% to 30%, whereas in low-resistivity wells, it is around 66%. These conditions result in adsorbed gas volumes of 60% and 30% for dry shale, respectively, underscoring the characteristic low adsorption capacity in low-resistivity shale. Besides the influence of macroscopic reservoir parameters on gas-bearing properties, microscopic pore structure also plays a significant role. Typically, a higher pore volume  
Figure 10: Gas-bearing characteristics of 1–3 sub layers of typical wells in the study area and their correlation with pore structure parameters. (**a**) typical well gas content column diagram; (**b**) typical wells proportion of adsorbed gas and free gas column diagram; (**c**) correlation diagram between pore volume and total gas volume, free gas volume, and adsorbed gas volume of the reservoir; (**d**) Correlation diagram between specific surface area and proportion of adsorbed gas. favors the storage of free gas, while a larger specific surface area enhances the adsorption of adsorbed gas. A correlation analysis of pore volume with total, free, and adsorbed gas content in typical shale reservoirs within the study area revealed a strong positive correlation between pore volume and both total and free gas content, with a weaker positive correlation observed with adsorbed gas content (Figure 10c). In low-resistivity shale reservoirs, smaller pore volumes (Figure 5a) are unfavorable for storing free gas. Due to its smaller pore radii (Figure 6) and larger specific surface area (Figure 5b), low-resistivity shale offers numerous adsorption sites, enhancing the adsorption of shale gas, causing a high proportion of adsorbed gas (Figure 10d). Thus, even with water saturation levels reaching 65% or even 80%, low-resistivity shale reservoirs still exhibit an adsorbed gas volume exceeding 1 m\({}^{3}\)/t. Based on the above analysis, it is believed that the main reasons for the low gas content in low-resistance shale reservoirs are high water saturation and low pore volume. From the analysis of the formation mechanism of low-resistance shale reservoirs, it is believed that the low pore volume is mainly due to the proximity of the reservoir to faults, which leads to the escape of shale gas and an increase in water saturation [30]. Under high temperature and pressure conditions, compaction and cementation are promoted, resulting in larger quartz particles, reduced pores, and decreased pore volume. Figure 11 shows that when the water saturation of shale reservoirs is less than 40%, the average pore volume is 0.0196 cm\({}^{3}\)/g; When the water saturation exceeds 40%, the pore volume rapidly decreases and eventually drops to 0.0074 cm\({}^{3}\)/g. According to relevant literature, as the burial depth increases, the porosity of shale reservoirs decreases slowly, and there is a phenomenon of increased porosity in some areas [31]. Meanwhile, the difference in burial depth of the shale reservoir studied is less than 200 m. So, the burial depth is not the main reason for the decrease in pore volume of shale reservoirs. Previous studies have shown that when the water saturation is high, in situ geological conditions can promote diagenesis, causing quartz mineral particles to increase and compress existing pores, resulting in a smaller pore volume [32; 33]. This study has recognized that low-resistivity shale reservoirs have a higher water saturation.