## 4 Conclusions  
We sought to reveal the law of water invasion in the multi-well development of sandstone gas reservoirs with strong water drives and to clarify residual gas distribution characteristics. Based on previous studies, this paper used the developed large-scale three-dimensional physical model to conduct water invasion simulation experiments under different water body multiples and production systems. The conclusions are as follows:  
1. Under the same production system conditions, the water invasion effect is heightened as the water body multiple increases. The strength of the edge and bottom water of the gas reservoir can be assessed by monitoring the change in the bottom hole pressure, allowing for the anticipation and prevention of potential water invasion risks. 2. In the late production stage, the water body rapidly advances along the fractures and high-permeability zones, resulting in gas wells waterflooding, lowering the ultimate recovery rate, and increasing the residual gas volume. Therefore, it is suggested that the low-position gas wells should be drained after water breakthrough to reduce the overall energy of water invasion, delay the water invasion rate in the high-position gas well area, improve the development effect, and increase the ultimate recovery rate of the gas reservoir. However, it is necessary to do an excellent job in treating produced water. 3. Under the same water body multiple conditions, shutting in the gas well immediately after water breakthrough reduces water production and increases the water-free production period but decreases the recovery rate. This production system is applicable  
Figure 23: The relationship between the experimental residual gas volume and the drainage–production ratio. (**a**) Fracture model; (**b**) fracture–high-permeability zone model. Figure 22: The water saturation distribution of the fracture–high-permeability zone model at the end of the experiment. (**a**) Three times water body; (**b**) seven times water body; (**c**) seven times water body (shut-in after water breakthrough). when the water treatment capacity of the gas reservoir is poor, as it aims to maximize the water-free recovery rate and obtain the maximum economic benefits. * The residual gas is mainly distributed around the fracture-high-permeability zone and at the edge of the gas reservoir. It is suggested that well pattern thickening be implemented or the drainage-production ratio be increased in the residual gas enrichment area, the residual gas volume at abandonment be reduced, and the recovery rate be increased. Conceptualization, S.H. and F.F. ; methodology, S.H. and J.Z. ([PERSON]); software, [PERSON] ([PERSON]); validation, [PERSON] ([PERSON]) and Y.B. ; formal analysis, [PERSON] ([PERSON]); investigation, S.H. and J.Z. ([PERSON]); resources, F.F. and Y.B. ; data curation, S.H. ; writing--original draft preparation, S.H. and F.F. ; writing--review and editing, S.H. and F.F. ; visualization, S.H. ; supervision, F.F. and Y.B. ; project administration, S.H. ; funding acquisition, S.H. and F.F. All authors have read and agreed to the published version of the manuscript. This research was funded by the Natural Science Foundation of Chongqing, CSTB2022 NSCQ-MSX1423, the Scientific and Technological Research Program from Chongqing Municipal Education Commission, KJQN202301537, the National Energy Shale Gas Research and Development (Experimental) Center Open Fund, 2023-KFKT-39, the National Energy Tight Oil and Gas Research and Development Center Development Fund, 2023-KFKT-11. Not applicable. The data presented in this study are available on request from the corresponding author. The data are not publicly available due to some data confidentiality restrictions. Author [PERSON] was employed by the PetroChina Jilin Oilfield Company. Author [PERSON] was employed by the Research Institute of Petroleum Exploration and Development.