## 4 Results
### Fracture Propagation Simulation During Refructuring
#### 4.5.2 Analysis of Key Controlling Factors in Refracturing  
One important strategy to improve the development effect of low-permeability reservoirs is repeated prefructuring reservoir recharge. The primary reason preventing production stabilization in the late stage of the first fracturing production is the quick depreciation of formation energy. To rebuild the formation energy system and achieve an increase in  
Figure 17: Refracturing fracture propagation locations and residual oil distribution. Figure 18: Correlation between refracturing fractures and microseismic events. Different colors indicate microseismic events corresponding to different stages. production, the fluid percolation theory states that large-scale fluid/gas injection and pressure boosting in the boring wells before refracturing can greatly increase the water-phase pressure and saturation in the near-well zone and restore the pore pressure of the reservoir in the low-pressure zone [48]. The fluid injection volume and the formation pressure recovery rate have a positive correlation, according to the numerical simulation results in Figure 19. Additionally, the pressure enhancement greatly increases the cumulative production growth of a single well, confirming the need for energy replenishment measures. The liquid injection pressure and single well deficit volume must be combined in the optimization approach to calculate the replenishment energy, with the injection pressure and injection ratio serving as the primary control parameters. According to field experience, two fundamental requirements must be fulfilled for effective make-up energy: the injection and extraction ratio must be more than two, and the injection and extraction pumping pressure must be higher than the pumping pressure following the first fracture. One important component influencing the efficacy of refracturing is stress field deflection. The direction and size of the stress field surrounding the well are dynamically adjusted because of the formation's elastic energy deficit following the first fracturing production [49; 50]. Changes in pore pressure cause the rock matrix to respond elastically, which leads to the creation of stress difference zones surrounding the horizontal well. The first fracture's end experiences stress concentration, while the wellbore's toe and heel cause the principal stress direction to deflect because of a change in positive stress, which directly regulates the extension path of the repeatedly fractured fracture. It is challenging to achieve fracture steering control just by depending on the natural stress field when the stress deflection amplitude is insufficient, as seen in Figure 20. Artificial intervention is required to increase the complexity of the fracture network through the temporary plugging process. Initial fracturing, fracture geometry, and completion design all affect the distribution of residual oil. Due to the vast spacing of segments and clusters and the modest scale of alterations, initial fracturing frequently produces simple biplane fractures with low fracture complexity, which results in an overall underutilization of the reservoir [51; 52; 53; 54]. After water injection, the interseam and near-seam portions of these cracks maintain substantial oil saturation, according to the numerical simulation above, indicating a sizeable  
Figure 19: Two formation recharges before YP 3 refracturing. **(a)** Pressure distribution of water vapor injection throughput experiment. **(b)** Pressure distribution of the CO\({}_{2}\) injection recharge experiment. residual oil potential. Multiple water injections can increase the amount of reservoir usage, but maintaining this potential is made more difficult by the considerable drop in oil saturation along the fractures following conventional throughput.