New Concept Discrete Fracture Network Model Simulator, GeoFlow, and Three Dimensional Channeling Flow in Fracture Network

Discrete fracture network (DFN) model simulations, where a fracture network can have a natural heterogeneity, is one of the most effective approaches in fluid flow analyses for naturally fractured and enhanced geothermal reservoirs. In the DFN model simulations, fractures are modeled by a pair of parallel smooth plates although real fractures have rough surfaces. Numerous field and laboratory observations have suggested that fluid flow through a fracture occurred in specific channels (channeling flow) due to a heterogeneous aperture distribution formed by the rough surfaces that are partially in contact with each other under a subsurface compressive stress field. The conventional DFN model simulations therefore give us a serious concern about the reality. To address this concern, we have developed a new concept DFN model simulator, GeoFlow, in which fractures can have heterogeneous aperture distributions. Three dimensional fluid flow simulations were performed for a simple fracture network by both the conventional and the new DFN modeling simulations. In the conventional DFN model simulation, fractures have no aperture distribution, and fluid flow in the fracture plane was therefore quite uniform, which was conflict with the filed observations. On the other hand, GeoFlow clearly showed formation of preferential flow paths in each fracture plane, developing three dimensional preferential flow paths in the fracture network.