Quantitative measures of image resolution for seismic survey design

Abstract

Illumination and fold analyses can provide valuable information for the design of seismic surveys, but generally they do not provide quantitative results that are directly related to the seismic images that would be obtained using a proposed acquisition geometry. On the other hand, the Beylkin (1985) equation predicts the spatial resolution of prestack migration using the acquisition geometry and an earth model, providing a simple yet effective tool for survey design. Calculations for a simple homogeneous earth model demonstrate the advantages of this approach. Specifically, the variations in spatial resolution within the model show that the best resolution results from singlefold, zero‐offset experiments for very simple acquisition geometries. Applications of the same design method to a realistic salt model show that some results are not surprising, such as decreases in resolution beneath the salt structure. However, the best resolution beneath the salt is obtained with the maximum offset for a trial single‐cable marine geometry, not the zero‐offset source–receiver pairs. This is a consequence of ray bending by the salt structure and the geometry of the acquisition lines. The result clearly demonstrates the utility of the proposed survey design tool. We also find that a land circular source/radial receiver line array design shows strong potential for improved resolution over the simple marine geometry. Furthermore, tests show that the land survey should display more robust results as the S/N ratio decreases.