Part II — CRS-beam PSDM: Kirchhoff-beam prestack depth migration using the 2D CRS stacking operator

Abstract

Beam-migration methods efficiently extend the benefits of Kirchhoff migration and enhance its imaging accuracy, producing high-fidelity images of complex geological structures . The common-reflection-surface (CRS) stack method produces zero-offset (ZO) sections with a high signal-to-noise ratio and better continuity of reflection events, particularly for dipping structures, from multi-coverage data. The CRS stacking operator depends on three kinematic attributes determined from prestack data with automatic optimization procedures. These attributes have several applications: velocity model determination via tomography , the determination of projected Fresnel zones, and time and depth migration. Following the concepts of the beam-migration methods, we present a new depth migration procedure, called CRS-beam prestack depth migration (CRS-beam PSDM), that combines Kirchhoff depth migration and the CRS stacking method. This new migration approach is based on the CRS stacking operator's ability to collect paraxial contributions around each reference trace amplitude that is to be migrated through the Huygens curve. The present migration algorithm was tested on a synthetic 2D seismic dataset containing reflections from the steeply dipping interfaces. The results obtained show significant improvements when compared to conventional Kirchhoff migration. The algorithm was also applied to prestack migrate a real, low-fold, 2D seismic line acquired in the Tacutu basin, Brazil. The comparison of our two final results demonstrates improvements to image resolution and quality; thus, our new method leads to more accurate geological interpretations. ► We present a new beam type prestack depth migration based on the CRS stack method. ► The CRS traveltime is used for the beam stack on the fly traces prior to migration. ► The aperture for the beam stack is estimated from the CRS attributes. ► The migrated energy is concentrated based on the dip and curvature information.