Numerical simulation of fracture network generation in naturally fractured reservoirs

In this study, numerical modeling of hydraulic fractures propagation is performed to analyze the forming mechanism of complex fracture network during the process of hydraulic fracturing in naturally fractured reservoirs. The model couples fracture deformation with fluid flow in the fracture network and horizontal wellbore. The enhanced 2D displacement discontinuity method is used to capture fracture deformation. When fracturing fluid fills the natural fracture before crossing happens, the interaction criterion between hydraulic fracture and natural fracture developed by Gu et al. (2012) is modified to incorporate fluid pressure in natural fracture. The implicit level set schemes based on tip asymptotical solution is presented to locate the fracture tips. Simulation results indicate that fracture spacing and stress anisotropy have significant influence on the propagation path and geometry of multiple fractures. Accounting fluid pressure drop in the wellbore will lead to asymmetrical geometry and stress shadowing effect of side fractures on the middle fracture when three-cluster fractures propagate simultaneously. Multiple fractures will be directed back to the maximum stress direction after long propagation length. Results show that stress shadowing effect and natural fractures are key controlling factors of complex fracture networks in unconventional reservoirs.