Abstract
A method to represent fracture networks as grid cell conductivities in a continuum model is described and evaluated. The method is developed for a sparsely fractured rock with a conductivity field that is dominated by major fractures and fracture zones. For such a fracture system it is believed that an accurate description of the correlation and anisotropy structure is essential. The proposed method will capture these features of the fracture system. The basic approach of the method is to evaluate accurate cell conductivity values for a staggered grid arrangement, i.e. velocities are stored at cell walls and scalars at cell centres. The balance of forces, i.e. the Darcy law, is evaluated for a control volume centred around the point where the velocity component is stored. Fractures are assumed to have a thickness and conductivity. The conductivity of a velocity control volume is calculated from the intersecting volume between the fracture and the velocity control volume. Intersecting volumes, with their respective conductivities, are added up to form the control volume conductivity. The general conclusion is that the method results in accurate simulations. It is expected that the method can be utilised in many practical groundwater simulations. This statement is based on the results from three test cases with analytical solution and one test case where results are compared with those from established theories.
Published Version
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