## 6 The Impact of Low-Resistivity Shale Reservoir Characteristics on Gas-Bearing Properties  
Gas content, serving as the foundation for shale gas resource assessments, has consistently been accorded significant importance by geologists as a crucial aspect of research, encompassing aspects such as storage space, total gas content, and the ratio of free to adsorbed gas. This not only influences the evaluation of shale gas resources but also impacts its extraction. During the examination of shale reservoirs' gas-bearing characteristics, besides analyzing the total gas content and the ratio of free to adsorbed gas, factors influencing the presence of shale gas within storage spaces and the distribution of adsorbed and free gas are also emphasized. This research primarily acquires the adsorbed gas of shale lithology via methane isothermal adsorption experiments [26], and computes the free gas content in shale reservoirs using parameters such as porosity, temperature, pressure, and water saturation. The detailed calculation methods are as follows [27]:  
\[n_{free}=\frac{PT_{sc}S_{g}\varphi}{ZTP_{sc}\varphi_{r}} \tag{4}\]  
In the formula, \(S_{g}\) represents the gas saturation, expressed in percentage; \(T_{sc}\), the standard ground temperature, set at 273.15 K; \(Z\), the gas compression factor; \(\varphi\), the porosity, also in percentage; \(P_{sc}\), the standard ground pressure, at 0.101 Mpa; and \(\rho_{r}\), the density of the gas-bearing rock, g/cm\({}^{3}\). The density of the free gas phase under specific temperature and pressure conditions can be determined using the equation of state, while the compression factor can be sourced from a table. The gas content of the shale reservoirs in the study area exhibits significant variation. Normal-resistivity wells exhibit a free gas content exceeding 5 m\({}^{3}\)/t, reaching up to 8.86 m\({}^{3}\)/t, with a lower adsorbed gas content ranging from 1.45 to 1.85 m\({}^{3}\)/t. Conversely, low-resistivity wells display lower free and adsorbed gas contents, with both being under 3 m\({}^{3}\)/t and 1.5 m\({}^{3}\)/t, respectively (Figure 10a). Clearly, the total gas content in normal-resistivity wells significantly surpasses that of low-resistivity shale gas wells, often being 2-4 times greater. Subsequently, the study calculated the proportions of free and adsorbed gas in both normal and low-resistivity wells. The findings reveal that adsorbed gas constitutes a larger proportion in low-resistivity wells, consistently surpassing 30%, compared to the 19.62% average in normal-resistivity wells. Figure 9: (**a**) The impact of the fault’s hanging wall and footwall, fault throw on resistivity; and (**b**) The correlation between the distance from the reservoir to the class II fault and the water saturation. A comparative analysis of the results revealed that low-resistivity wells have a relatively low gas content, comprising both adsorbed and free gas volumes, but with a disproportionately high proportion of adsorbed gas. This investigation focuses on elucidating the underlying reasons for this phenomenon, examining both the macroscopic properties and the microscopic pore structure of the reservoirs. The macroscopic characteristics of low-resistivity wells include high clay content and high water saturation, as indicated in Table 1. According to Equation (3), the content of free gas is primarily influenced by temperature, pressure, porosity, and gas saturation. The study area has a considerable burial depth, with minimal variations in temperature and pressure. The key determinants of free gas quantity in shale reservoirs are porosity and water saturation, primarily accounting for the low free gas levels in low-resistivity shale reservoirs. The influence of water saturation on adsorbed gas should be differentiated from its effect on free gas. For free gas, formation water primarily fills pore spaces, diminishing its storage capacity. For adsorbed gas, formation water forms a film on pore walls, occupying methane's adsorption sites, thus lowering the adsorbent's capacity [28].