Fracture analysis in the Amellago outcrop and permeability predictions
Résumé
Field observations from several outcrops in the Eastern High Atlas Mountains, near Amellago (Morocco), are used to determine fracture-network model parameters, such as the aspect ratio of the fractures represented as rectangles whose longer side is horizontal, the volumetric area of fracture surfaces, the fracture mean size and the fracture density. The fracture orientations can be roughly approximated by Fisher distributions, where the parameters are determined by outcrop measurements. The permeability of the fracture networks can be calculated by application of the Snow equation for infinite fractures or by numerical resolution of the flow equation for fracture networks generated with the parameters deduced from the outcrop measurements. These two permeability estimations are shown to be in good agreement, which suggests that theoretical or semi-empirical solutions may provide reasonable approximations of fracture-network permeability in some carbonate reservoirs when conditioned to appropriate outcrop and subsurface data.