# Simulation of Gas Fracturing in Reservoirs Based on a Coupled Thermo-Hydro-Mechanical-Damage Model
## 4 Analysis of Numerical Simulation Results
### Impact of Parameter Variations on the Efficiency of Rock Extraction  
Due to the countless points and lines within the unit cell, it is impossible to sequentially conduct simulation analysis at all positions. Therefore, a straight line was selected along the boundary of the unit cell and the borehole boundary. In this way, the data analysis conducted on this line can represent the simulation situation at any position within the unit cell. The selection of the line segment within the unit cell is shown in the Figure 8.  
As shale gas is considered a fluid and follows Darcy's law, there exists Darcy velocity within the specimen. Since the extraction of shale gas occurs from the wellbore outward, integrating the gas velocity around the wellbore yields the instantaneous gas extraction rate of shale gas. By accumulating the instantaneous extraction rates obtained through integration, the temporal variation of shale gas extraction can be determined. To investigate the influence of different temperatures on shale gas extraction efficiency, this study selected four different temperatures. Simulations and analyses were conducted on the gas content at different positions under various temperatures to demonstrate the effect of temperature on shale gas extraction efficiency from a lateral perspective. From Figure 9, it can be observed that the gas content of samples varies with position along the wellbore at different temperatures. When the temperature is low, the change in gas content over time at the same position is not significant. However, at higher temperatures, the difference in gas content at the same position but at different times gradually decreases as the temperature rises. Additionally, at higher temperatures, the gas content at the same position and time is higher. This indicates that as the temperature increases, the efficiency of gas fracturing gradually improves. At the same time, the degree of rock fragmentation increases with temperature, leading to an increase in gas permeability. The gas content at the same position and time increases, further demonstrating that temperature can enhance gas fracturing efficiency. Figure 8: The entire unit was simulated using a line within the unit cell to represent the overall situation. From Figure 10, it can be observed that with increasing temperature, the gas content near the drilling location decreases significantly. However, the gas content near the boundary positions shows an increase. This phenomenon indicates that under the influence of temperature, gas molecules exhibit more active movement as the temperature rises. Therefore, it can be inferred that shale gas extraction can be more efficient in rock formations with higher temperatures. The experimental results indicate that the gas content of the specimens exhibits an upward trend as the analysis position is situated further away from the wellbore, as illustrated in the Figures 11 and 12. Additionally, with an increase in the volumetric constant VL of the specimens, the gas content at the same position also exhibits an upward  
Figure 10: The relationship between gas content along the wellbore and different temperatures at the same time. Figure 9: The gas content at different positions and times along the wellbore is influenced by varying temperatures. trend. This indicates that during gas fracturing, the gas surrounding the borehole is rapidly depleted, leading to a significant decrease. However, the gas content within the undisturbed rock mass remains relatively unchanged. Furthermore, it can be inferred that an elevation in the VL value corresponds to increased challenges in gas fracturing, ultimately resulting in a reduction in shale gas extraction efficiency. Based on the depicted Figures 13 and 14, it becomes apparent that the gas content of the specimens exhibits a rising tendency as the analysis position distances itself from the wellbore. Conversely, with an increase in the PL parameter of the specimens, the gas content at the same position exhibits a decreasing trend.