An IFS-based fractal discrete fracture network for hydraulic fracture behavior of rock mass

Abstract

The discrete fracture network (DFN) model is applied for fluid flow and transport simulations in fractured rock masses. In this study, a novel two-dimensional fractal DFN generation method was proposed based on the iterative function system (IFS). To achieve the fine mesh for the DFN model, a refinement technique was presented to remove the short edges and small gaps. Subsequently, the zero-thickness flow cohesive element was inserted at the adjacent edge of elements for the hydraulic fracture modeling. The results indicated that the injection pressure of hydraulic fracture had three phases: Sudden increase, rapid drop-off, and stabilization. Compared with the traditional linear DFN model, the injection pressure evolution and fracture propagation of fractal DFN were significantly affected. In addition, the fracture aperture variation was an important factor influencing hydraulic fracturing in the rock mass. Considering the complexity of the hydraulic fracturing process, the effects of mesh sensitivity and fracture aperture size were also analyzed based on two-dimensional simulation results. This study presents a novel 2D DFN model for an accurate description of fracturing and provides a valuable simulation method for hydraulic fracturing.