Faults that affect fluid flow in hydrocarbon reservoirs are produced by the deformation of a large variety of sediment types under different stress conditions. Deformation processes comprise grain reorientation, clay smear and cataclasis.Anew ring shear device was constructed in order to investigate experimentally deformation processes in sediments during faulting and consequent effect on fluid flow. Three main types of shear bands are observed from the experiments: 1. Sand shear in areas with sand-sand juxtaposition. Grain size reduction is strongly dependent on the burial depth during shearing. 2. Clay smear mixed with sand grains, typically for shallow burial depth. 3. Complex shear zones made of clay and sand shear with massive grain crushing on both sides of the clay smear, typically for greater burial depths. At shallow burial depth, clay smear is the main mechanism responsible for permeability reduction as sand- sand juxtaposition shear is dominated by grain rolling causing only minor permeability reduction.At greater burial depths, permeability reduction is dominated by grain crushing.
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