Fluid Flow through Rough Rock Fractures: Parametric Study

The knowledge of fluid flow through rock fractures is directly related to hydrocarbon migration, waste disposal, and carbon dioxide sequestration. The hydraulic nature and response of the fractures are directly controlled by the roughness of the fracture surfaces. However, this parameter is hard to understand because it can behave differently under different ambient conditions. The prevalent controlling parameters are the fracture inflow pressure, aperture of the fracture, and shearing displacement during flow. To understand the influence of these parameters, a systematic study was carried out numerically on different fracture geometries. In this paper, two-dimensional fractures with different surface roughness were simulated in a finite-element modeling (FEM) program, and the fluid-flow parameters were evaluated. The Navier-Stokes (NS) equation was used to model the fluid flow through the roughness profiles generated using Barton's joint roughness coefficient. By simulating the laminar fluid flow through the NS equation and predicting the particle transport using a streamline particle-tracking method, the flow-velocity profiles, outlet-pressure distribution, Reynolds number, shear rates, and particle transmissivity were measured. The parameters at different locations along the length of the fractures were compared to identify changes in the fluid flow. The models show that local undulations have considerable effect on the fluid flow. The velocity and shear-rate evolution, pore-pressure distribution, and Reynolds number of the flow indicate the presence of a strong wall effect on the fluid flow. The aperture and shearing displacements of the fracture walls also have significant control over the wall effect. (C) 2015 American Society of Civil Engineers.