Abstract
The clear understanding of hydraulic fracture network complexity and the optimization of fracture network configuration are important to the hydraulic fracturing treatment of shale gas reservoirs. For the prediction of hydraulic fracture network configuration, one of the problems is the accurate representation of natural fractures. In this work, a real natural fracture network is reconstructed from shale samples. Moreover, a virtual fracture system is proposed to simulate the large number of small fractures that are difficult to identify. A numerical model based on the displacement discontinuity method is developed to simulate the fluid-rock coupling system. A dimensionless stress difference that is normalized by rock strength is proposed to quantify the anisotropy of crustal stress. The hydraulic fracturing processes under different stress conditions are simulated. The most complex fracture configurations are obtained when the maximum principle stress direction is perpendicular to the principle natural fracture direction. In contrast, the worst results are obtained when these two directions are parallel to each other. Moreover, the side effects of the unfavorable geological conditions caused by crustal stress anisotropy can be partly suppressed by increasing the viscous effect of the fluid.
Highlights
The dense spacing hydraulic fracture network is important for shale gas reservoirs [1,2]
These results indicate that stress difference is better in quantifying the stress anisotropy that related to fracture network configuration
A natural fracture network can be well represented by identifying the fracture trajectory directly from rock samples along with a virtual fracture system
Summary
The dense spacing hydraulic fracture network is important for shale gas reservoirs [1,2]. As the simulation domain is often several orders bigger than the aperture of fractures, a deformation that is considered as small “noise” in a solid solver may induce dramatic oscillations of fluid pressure in a flow solver [19] As a result, these methods are ill-conditioned for the fluid-rock coupling system of hydraulic fracturing. These methods are ill-conditioned for the fluid-rock coupling system of hydraulic fracturing Another problem is the complexity of grid re-meshing, which is necessary for the accurate simulation of fracture trajectory [20]. A DDM-based numerical model is developed to investigate how hydraulic fracture networks propagate under different stress conditions and how to get complex hydraulic fracture network by adjusting the viscous effect of the fluid
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