Late Cretaceous-cenozoic exhumation of the Faroe-Shetland basins along the NW Atlantic margin

Abstract

Very generally speaking, foliation describes a pervasive planar feature within a rock mass (e.g. caused by preferred orientation of minerals). Borehole image log data comprise the only way to see such sub-seismic features. The data can be used for the determination of foliation and to analyze its orientation and characteristics. The appearance of foliation in borehole image logs is rather blurry and does not show the sharp conductivity changes that fractures generally do have. The anisotropy of rocks caused by foliation as well as the influence of foliation to the fracture network has been dramatically underestimated in the past. By analyzing borehole image log data of over 25 wells in fractured basement reservoirs, we can show that foliation influences fracture orientation. It is evident that anisotropy caused by foliation does have an effect on the mechanical properties of the rock mass, which in turn influences the permeability and productivity of a reservoir rock. We can further show that the anisotropy of mechanical parameters caused by foliation influences the later formation of natural fractures in the intact rock and potentially impedes straight forward geomechanical modeling...