# Hydraulic Expansion Techniques for Fracture-Cavity Carbonate Rock with Field Applications
## 4 Conclusions  
1. After long-term exploitation of wells, the insufficient energy in the formation of fractured carbonate reservoirs leads to a rapid decrease in production, and the water content of crude oil steadily increases. Hydraulic expansion of the fractured carbonate rock may connect fractures and pores that were not affected by the original production, allowing the internal raw oil to enter the production fractures and replenish energy.
2. For wells with multiple sets of well-developed fractures and cavities in the surrounding area, we apply high pressure to prevent nearby fracture networks from opening and connecting to distant fracture and cavity reservoirs. When controlling karst with clay-filled faults, we increase the injection rate to generate diversion and spread to the remaining non-eroded fracture areas. For wells with insufficient fluid supply after pre-acidification fracturing, we activate sealed or partially sealed original high-permeability channels by applying high pressure.
3. Considering temporary plugging and acid fracturing, we also propose (1) temporary plugging of the main deep fractures, followed by hydraulic expansion, and (2) composite expansion and acidification/compression processes.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Water Injection Type** & **Injected Water (m\({}^{3}\))** & **Water Pressure (MPa)** & **Cycle Fluid** & **Cycle Oil** & **Cycle Water** & **Production** & **Fluid Produced per** \\
**Production** & **Production** & **Production** & **Content** & **Pressure Drop** & **Unit of Pressure Drop** \\
**Production** & **(m\({}^{3}\)/MPa)** & **(m\({}^{3}\)/MPa)** & **(m\({}^{3}\)/MPa)** & **(m\({}^{3}\)/MPa)** \\ \hline Round three of regular water injection & 3887 & 15 & 5863 & 3221 & 45 & 29 & 201 \\ First round of high-pressure hydraulic expansion & 9361 & 23 & 2084 & 917 & 56 & 32 & 66 \\ Second round of high-pressure hydraulic expansion & 20,404 & 19 & 14,429 & 13,804 & 4 & 26 & 547 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Production obtained from conventional and high-pressure hydraulic expansion.  
4. Hydraulic expansion allows us to recover and supplement the formation energy and efficiently increase production. We tested various wells, achieving an effective hydraulic expansion rate of up to 85%. In addition, the productivity of conventional water injection and hydraulic expansion after on-site construction was evaluated for one well, clearly indicating the effectiveness of water injection and the remarkable increase in crude oil production after hydraulic expansion.  
Conceptualization, J.L., methodology, J.L. and W.L.; validation, J.S.; formal analysis, J.L. and J.S.; writing, J.L. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the Scientific Research Project \"Research on the micro mechanism and treatment method of aging oil containing polymer residue\" of the China University of Petroleum (Beijing) at Karamay under grant number XQZX20210005.  
Not applicable.  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
The authors declare no conflicts of interest.