Investigation of the propagation behavior of hydraulic fractures and its influencing mechanisms in fractured reservoirs based on a hydromechanical coupling numerical model

Numerous discontinuities, such as bedding planes and natural fractures, occur in reservoir rocks and significantly influence the propagation behavior of hydraulic fractures during reservoir stimulation. To elucidate the mechanisms underlying the influence of natural fracture networks in reservoir rocks on the propagation of hydraulic fractures, a finite element–discrete fracture model is employed to establish a fluid–solid coupled finite element–discrete fracture model. This model is used to investigate the propagation behavior of hydraulic fractures in fractured reservoirs and their underlying mechanisms. The results indicate that when distant from natural fracture networks, hydraulic fractures typically propagate along the direction of the maximum principal stress. Upon approaching natural fracture networks, the propagation path of hydraulic fractures is altered, leading to localized deflection. The mechanical properties of the rock matrix versus those of natural fracture networks, in situ stress, fracturing fluid viscosity, and injection rate significantly influence the propagation of hydraulic fractures in fractured reservoirs. Increased mechanical disparity between the rock matrix and natural fractures promotes deflection along natural fracture networks, resulting in the formation of complex fracture networks. However, increased in situ stress, fracturing fluid viscosity, and injection rate facilitate direct penetration of natural fractures by hydraulic fractures, yielding the formation of simple, long, straight primary fractures. Furthermore, the propagation distance of hydraulic fractures along the direction of the maximum principal stress is positively correlated with the in situ stress, fracturing fluid viscosity, and injection rate. The findings of this study provide theoretical guidance for optimizing fracturing design.