The influence of natural fractures on the propagation of hydraulic fracture in fractured reservoirs was studied by laboratory tests. During the test, a 300mm × 300mm × 600mm cement specimen with a number of natural fractures was used to simulate the fractured reservoirs. The specimens under different conditions such as in-situ stress, natural fracture size, rate and viscosity of fracturing fluid were tested to obtain the relation chart of hydraulic fracture morphology and in-situ stress and natural fracture size. According to the complexity, the hydraulic fracture was divided into three categories: fracture networks, branched fractures and a single fracture. The results show that the larger the size of natural fractures, the smaller the in-situ stress difference, the easier to form fracture networks when hydraulic fracturing. For natural fractures of any size, the fracturing will not form fracture networks when the in-situ stress difference is greater than 8MPa; the natural fractures will not have an impact on the hydraulic fracture when the in-situ stress difference is greater than 14MPa. At the same time, the hydraulic fracture will be fracture networks with small viscosity and rate of fracturing fluid. The above conclusions have important reference significance for the fracturing design of fractured reservoirs.

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