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Unconventional oil and gas resources serve as vital replacement energy in China’s hydrocarbon portfolio, and their efficient development is of great significance for safeguarding national energy security. The implementation of staged multi-cluster hydraulic fracturing in horizontal wells, along with the optimization of intra-stage cluster design parameters, is critical to maximizing the production potential of unconventional reservoirs. Clarifying fracture propagation mechanisms and quantifying the relationship between fracture geometry and well productivity is key to optimize intra-stage multi-cluster fracturing strategies. In this study, a phase-field method is employed to simulate the competitive propagation morphology of multiple fractures within a fracturing stage. A fracture morphology identification technique is integrated to construct a two-dimensional equivalent fracture model, which can characterize the stimulated flow pathways. Equivalent physical parameters after stimulation are extracted and transferred-together with geometric descriptors-as input for a discrete fracture flow model. This enables automatic coupling and data transfer between the geometric and flow models, thereby facilitating quantitative evaluation of production performance under different fracturing scenarios and ultimately achieving fully coupled fracture propagation-fluid flow simulation. The accuracy and feasibility of the dual-model coupling method are verified through comparison with laboratory-scale physical simulation experiments and field fracturing data. On this basis, the effects of intra-stage cluster number and cluster spacing on fracture morphology and production response are further investigated. The results show that, as the cluster spacing increases from 15 m to 25 m, the fracture deflection point shifts farther from the wellbore, and the tip deflection angle decreases from 30° to 24°. Meanwhile, the pressure gradient around the fracture tip is reduced, weakening the fluid driving force and significantly diminishing inter-fracture fluid interference. This change leads to a decline in peak daily oil production and stabilized production rate, with daily and cumulative oil output decreasing by 35.88% and 35.89%, respectively. In contrast, when the number of clusters per stage increases from 3 to 5, the deflection angle at the tip of the outer fractures increases from 30° to 34°, while the coverage of the induced stress field expands from 36.74% to 42.46%. This results in a higher pressure gradient surrounding the fractures, enhancing the fluid driving force and significantly improving oil mobilization. Consequently, peak daily and cumulative oil production increased by 40.49% and 45.467%, respectively. Therefore, optimizing the intra-stage cluster spacing and cluster number can effectively balance the degree of fracture interference and enhance single-well productivity, thereby improving the overall effectiveness of staged multi-cluster hydraulic fracturing in horizontal wells.
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