Summary Deep coalbed methane (CBM; more than 1,500 m in depth) has attracted worldwide attention since production breakthrough has been achieved recently. Hydraulic fracturing plays an important role in productivity enhancement. To further enhance the stimulation efficiency, oriented perforation has proved to be an effective way to optimize the fracture initiation and propagation directions, maximize cluster efficiency, and mitigate proppant/sand/coal particles flowback into horizontal wells. Therefore, it is of great theoretical value and practical significance to study the optimization of oriented perforation parameters for horizontal wells in deep CBM with geological specialties. Here, we establish a 3D numerical model based on the finite discrete element method (FDEM) approach to simulate the oriented perforation fracturing performances. The accuracy of the model is confirmed by analytical solutions. Subsequently, we performed a series of parametric studies to quantitatively analyze the fracture geometries, volume, and stimulated reservoir volume (SRV) under various oriented perforation patterns, perforation numbers, pump rates, and natural fractures in deep CBM wells. Finally, we investigated field cases in seven actual horizontal wells located at the Nos. 8 and 9 coal seam (1,950 m in depth), Shenfu deep CBM field, Ordos Basin. The field applications further shed light upon the oriented perforation strategies and optimization decisions. Implications and suggestions were also provided for field treatments to enhance the stimulation efficiency. The results demonstrate that the oriented design achieves higher stimulation efficiency than the nonoriented designs since hydraulic energy can be focused on stimulating the target areas. The integration of oriented perforation with limited-entry designs could further enhance the directional stimulation effect. Assisted by downhole microseismic monitoring data, oriented perforation can direct the fractures to grow in height and connect to the target sweet spots. Production rates in the wells completed with oriented perforation designs outperformed those of the wells completed with nonoriented perforation designs, owing to the improved communications with the geological sweet spots, especially with bright and semibright coals. Furthermore, enhancing the suitability of oriented perforation patterns with geological sweet spots, coal types, and wellbore trajectories can increase the portion of propped fractures and further augment the gas productivity. These findings underscore the importance of customizing perforation strategies by considering the geological conditions and actual well trajectories to maximize the production potential in deep CBM horizontal wells. This study provides both theoretical insights and practical guidance for improving the fracturing efficiency in deep CBM reservoirs.
Yang et al. (Thu,) studied this question.