Hydraulic fracturing treatment has been proven to be one of the key technologies for shale gas development. Micro-seismic mapping data has shown that hydraulic fracturing stimulation has often resulted in complex fracture network due to the geological complexity of shale formations. Hydraulic fracturing is a coupled process of shale formation deformation and flow of engineered fluid that includes water, proppant and other chemicals. Moreover, the pre-existing natural fractures in shale formation may complicate hydraulic fracture propagation process and alter its Young’s modulus. In this paper, we have developed a numerical model for modeling hydraulic fracture propagation in highly fractured shale formation. The proposed numerical model has integrated turbulent flow, rock stress response, interactions of hydraulic fracture propagation with natural fractures, and influence of natural fractures on formation Young’s modulus. Mixed finite element method is employed for numerical solution of the nonlinear partial differential equations. The proposed model has been validated with bi-wing hydraulic fracture model through regression tests. The preliminary numerical results illustrate the significant differences in modeling hydraulic fracture propagation in comparison with current models that assume laminar flow in hydraulic fracture process. Two simulated cases with different initial natural fracture mapping are given. The preliminary numerical results show that length and density of natural fracture have significant impact on formation Young’s modulus, and interactions between hydraulic fracture and natural fractures create the complex fracture network. This model provides an opportunity to optimize hydraulic fracturing stimulation design through numerical simulations, which is vital in shale reservoir development.
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