## 5 Conclusions  
To solve the problem of production decline after the initial fracturing of shale oil horizontal wells, we present a numerical simulation technique for refracturing based on a three-dimensional fully linked seepage field-stress field model. The orientation and duration of fractures during repeat fracturing can be accurately predicted by examining the stress field deflection during the production process. This enables the control of the directional fracture propagation of intricate fracture networks and the effective use of leftover oil. The following are the primary findings of the study:  
(1) A single fracture 70 m after the initial fracturing is found to be difficult to make enough contact with crude oil for exploitation, based on the initial fracturing fracture propagation model and production dynamic analysis. To improve fracture complexity and half-length, it is imperative to re-select an efficient geo-geo-geo-engineering sweet spot for secondary fracturing. This is because stress disturbance after reservoir recharge fails to reach the residual oil-rich area.  
(2) A coupled seepage field-stress field model is developed based on the examination of well production dynamics and the initial fracturing model. According to our research, reservoir recharging ought to take place before recurrent fracturing, and it is necessary to ascertain the stress field's deflection angle. According to this study, the stress field's deflection angle should be between 30 and 50; if it is less than that, it is crucial to use diverting technology to increase fracture complexity.  
Figure 20: Effect of stress deflection on fracture propagation in refracturing. (**a**) Distribution of stress field produced after initial fracturing. (**b**) Effect of stress field on fracture extension in refracturing. The arrows represent the orientations of in-situ stress.  
(3) A model for fracture extension for recurrent fracturing, and numerical simulations shows that after optimization, the fracture length rises to 97-154 m. After refracturing, the volume of reservoir reforming is 125% larger than in the first stage, with the direction of the stress field guiding the direction of fracture extension. This maximizes the efficient use of residual oil and efficiently mobilizes it in hitherto untapped locations, offering insights into the extension of fractures during refracturing exploitation.  
Conceptualization, H.L. and G.H.; methodology, H.L., P.B. and G.H.; software, X.Y. ([PERSON]) and Y.Z. ([PERSON] 1); validation, P.B., Z.M., Z.P. and F.G.; formal analysis, X.Y. ([PERSON]), Y.L. ([PERSON]) and C.G.; investigation, H.L., Z.M., X.Y. ([PERSON]), J.R. and D.W.; data curation, X.B., Y.Z. ([PERSON] 2) and Y.L. ([PERSON]); writing--original draft, H.L.; writing--review and editing, P.B. and G.H.; supervision, P.B. and G.H. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Science and Technology Project of PetroChina (2023 ZZ28) and the Science Foundation of China University of Petroleum, Beijing (No. 2462023 BJRC001).  
Dataset available on request from the authors.  
Authors [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON] were employed by the company CNPC Research Institute of Petroleum Exploration and Development. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.