Hydraulic properties of 3D crossed rock fractures by considering anisotropic aperture distributions

Abstract

Abstract:This study presents a numerical study on the geometrical and hydraulic properties of a three-dimensional intersected fracture model that is a fundamental element involved in complex fracture networks. A series of rough fracture surfaces were generated using the modified successive random additions (SRA) algorithm. Different shear displacements were applied to the fracture to obtain the anisotropic aperture fields that will be further assigned to the two fractures in the intersected fracture model. The flow was calculated using the Reynolds equation with the continuity conditions addressed at intersection part between the two fracture planes. The evolutions of the aperture distributions, flow channels and equivalent permeability were estimated. The simulation results reveal that as the shear displacement and joint roughness coefficient (JRC) increase, the aperture increases anisotropically, which causes significant fluid flow channeling effects. The main flow channels change from being concentrated in one fracture to the other fracture during the shear, accompanied by the change of the flow rate ratios between two flow planes at the inlet/outlet boundary. During the shear the average contact area accounts for approximately 4% to 15% of the fracture planes, and the actual calculated flow area is about 35% to 42% of the fracture planes, which is smaller than the noncontact area. As the shear displacement and JRC increase, the equivalent permeability of the intersected fracture increases. Therefore, the channeling flow should be considered to interpret the fluid flow through the rough fractures even in the simplest fracture networks.

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