Publications

In geological situations where there is a complex overburden and poor signal to noise, Kirchhoff migration, which cannot handle multi-arrivals, often fails to produce good images of the subsurface structure. Downward continuation methods are able to handle multi-arrivals, but their inability to image steep dips is a severe limitation. We present a Beam migration which relaxes the single arrival limitation of Kirchhoff while retaining its steep dip capability. Our implementation of Beam migration is unique in the industry and involves a decomposition of the data into dip components using the Radon transform and a back-propagation of the dip components into the earth. The dip components can be enhanced based on various criteria before the backpropagation, thereby giving a more coherent image. The methodology inherently allows the attenuation of multiple energy, and coherent as well as non coherent noise. This powerful filtering capability is performed in migrated space, before reconstruction of the final image volumes. The migration method establishes a point-to-point mapping between the unmigrated and migrated centers of each seismic wavelet, with the mapping function being the earth velocity model. Model refinement proceeds via iterations of tomographic velocity updating. Results from the Beam migration are proving to be superior to Kirchhoff and wave equation results in several respects. The quality and flexibility of our implementation of Beam Migration is illustrated in many ways. These include its unique capability for handling steep and overturned dip, its demultiple options, the ability to handle extraneous coherent noise, and the adaptability to anisotropic velocity earth models. Also of importance is the speed for model iteration, allowing multiple iterations to be run where alternative methods are typically constrained to fewer iteration.