Abstract: Fracture network conductivity is one of the key factors for achieving efficient shale gas development,yet its influencing factors and evolution patterns remain unclear.To evaluate the conductivity of fracture networks with different structures,a proppant conductivity evaluation device was used to determine the variation patterns of fracture network conductivity under different numbers of branch fractures,different included angles between branch fractures,and different propping types.On this basis,and following the hydraulic-electric analogy principle,a prediction method for fracture network conductivity was established.The results show that the greater the number of branch fractures and the smaller the included angle between branch fractures and the main fracture,the higher the fracture network conductivity.Under low closure pressure,the conductivity of self-propped fracture networks is greater than that of propped fracture networks,whereas under high closure pressure,propped fracture networks are significantly superior to self-propped fracture networks in conductivity.Based on the established prediction model for fracture network conductivity,the calculated values agree well with the experimental values,with an overall root-mean-square error of 10.22%.These results can provide theoretical guidance for the formation of complex fracture networks with high conductivity during volume fracturing of shale gas reservoirs.

Key words: fracture network conductivity, branch fracture, self-propping, conductivity prediction