关键词:  页岩气, 水力压裂, 数值模拟, 离散元, 天然裂缝, 裂缝间距 

Abstract:  The shale gas reservoir has the characteristics of natural fracture development and strong heterogeneity, the continuum model can not be used to accurately characterize the shale reservoir. Based on the discrete fracture network ( DFN) model and seepage stress coupling numerical algorithm, a numerical model of the network fracture for modeling the complex interactions between created hydraulic fractures and natural fracture system is established, to analyze the effects of the hydraulic fracture spacing, mechanical properties parameters on the fracture network extension and connectivity. Results show that no matter how natural fracture networks distribution or artificial hydraulic fracture length, the formation of the secondary fractures can stabilize the shear failure zone of natural fractures at the top of the initial hydraulic fractures. The larger the aperture of the natural fractures at the tip of hydraulic fractures, the greater the fracture spacing, the greater the shear failure area, the possibility of fracture network connection far away from well is larger if  fracture spacing within a certain range. The smaller the internal friction angle of the fracture, the greater the connected area of the natural network, the more easily the complex fracture network formed. The connected area of the complex network fractures is different under the condition of different natural fracture dip angle combination. Numerical simulation results can provide theoretical basis for the prediction of complex network fractures in shale gas wells.

Key words:  shale gas, hydraulic fracturing, numerical simulation, discrete element method ( dem), natural fracture, fracture spacing