3D characterization of fracture systems using Terrestrial Laser Scanning: an example from the Lewisian basement of NW Scotland
Fractured gneiss lithologies form a basement-cored high, the Rona Ridge in the Faroe Shetland Basin. Basement structures are known to play an important role in the petroleum system for the overlying giant Clair Field. An onshore analogue exposure in the Lewisian Gneiss Complex at Kinlochbervie in NW Scotland provides an example of a hanging-wall damage zone of a large basement-hosted normal fault. In this study, we used remote sensing (2D), outcrop line sample methods (1D) and a virtual outcrop created by terrestrial laser scanning methods (3D) to characterize spatial variations of the fracture systems. Spacing distributions from 1D line samples collected from exposures and pseudo-wells constructed through the virtual outcrop show powerlaw distributions. The virtual outcrop data enable us to extend the scale-invariant description from 1 to 3 orders of magnitude. We developed a novel box-counting workflow to provide an assessment of 2- and 3D variations in the fracture properties. Fracture density and fractal dimension are elevated whereas the number of intersections is decreased within a 220 m-wide volume adjacent to the fault. We discuss how the methods and results from this study can aid the development of analogue for basement reservoirs in the offshore UK continental shelf.