Introduction To Subsurface Imaging PDF Download

(Cont.) The reduced spatial coverage limits the extent of the migrated image, precluding an evaluation of the effectiveness of the random receiver spread. The limited nature of the receiver array also caused artifacts resembling migration smiles in the image. These artifacts are partially suppressed by limiting the aperture of the migration, but this also removes dipping reflectors from the image. To maximize the imaging capabilities of the data, a second approach complimenting the GRT method is developed. This approach, termed vector image isochron (VII) migration, removes array artifacts from the image without losing energy from dipping reflectors. This allows artifacts in the conventional image to be identified, aiding interpretation of the GRT images. VII images also show more even illumination than conventional images, although an effect similar to NMO stretching reduces the resolution of the VII image as compared to the GRT image. The VII scheme is an extension of the GRT migration process of Miller et al. (1987), but involves forming an image which depends on the imaged plane orientation, transforming the image based on the array geometry, then finishing the GRT summation over plane orientations. The VII imaging method is derived in both 2D and 3D with the assumption that the ray paths are straight and that at least one of the arrays, source or receiver, is horizontally oriented. The surface array can have any distribution, regular or random. The other array can have any orientation in general, although this thesis assumes that it will be either another surface array or a vertically oriented borehole array. ...