## 5 Genetic Mechanism of Low-Resistivity Shale Reservoir
### Resistivity Response to Reservoir Macro Parameters  
This study utilized shale samples from various resistivity wells within the study area for rock-electrical experiments using brine with a saturated formation salinity of 23,000 mg/L. Experimental results are depicted in Figure 7. Shale samples from the normal-resistivity Well Y101H3-8 display high resistivity in their dry state, with values surpassing 1000 \(\Omega\cdot\)m, whereas the resistivity for low-resistivity shale gas wells (Well L211 and JYT1) is under 100 \(\Omega\cdot\)m. This suggests that the rock structure and mineral composition significantly influence resistivity (Figure 7a). The low-resistivity of dry samples from low-resistivity shale wells can be attributed to the higher clay mineral content, which enhances conductivity through internal structural water. A comparison between dry shale samples, their original states, and logging resistivities reveals that both the original state and logging resistivities are reduced compared to the dry state, highlighting the significant role of pore fluid under formation conditions in resistivity reduction.  
To eliminate the impact of porosity on resistivity, shale samples from various wells with porosities between 4% and 5% were chosen for resistivity tests at varying water saturations. The findings revealed that as water saturation rose, resistivity declined, yet notable disparities in resistivity were observed across different wells. After saturation of the shale samples to SW = 100%, it was observed that the resistivity of samples from normal resistivity wells was below 100 \(\Omega\cdot\)m, and those from low resistivity shale gas wells had resistivities below 10 \(\Omega\cdot\)m (Figure 7b). Consequently, high water saturation plays a significant role in contributing to the low resistivity of shale reservoirs. Furthermore, the normal-resistivity well transitions from its original resistivity to the saturated water resistivity, with a more pronounced decrease in resistivity than that observed in low-resistivity shale samples. This  
Figure 6: Bar chart illustrating the relationship between pore volume and pore size distribution within shale reservoirs of normal-resistivity wells and low-resistivity wells in the Luzhou area.  
is attributed to the higher water saturation in the low-resistivity shale samples under their original formation conditions, which sees less significant increase in water saturation when reaching 100%. Conversely, when the normal-resistivity shale gas well reaches 100% water saturation, the internal pore fluid increases by over 60%. Concurrently, the resistivity of 100% saturated water in low-resistivity shale samples is approximately several times lower than that of normal-resistivity samples. This suggests that besides the conductivity of pore fluids, the rock matrix is also a significant factor in reducing resistivity under water-bearing conditions. Elucidating the microscopic distribution of rock minerals can aid in unveiling the microscopic origins of low resistivity. Our understanding is consistent with the research findings of [PERSON] et al. (2022) and [PERSON] et al. (2022) [23; 24].