Orthorhombic velocity model building and imaging of Luda field with WAZ OBC data

Abstract

Summary Ocean Bottom Cable (OBC) acquisition has become the new trend in Bohai area with the benefit of operational flexibility, better illumination, better multiple elimination and better S/N for the targets at middle to deep depth. However, the presence of azimuthal anisotropy can cause severe imaging challenges in the Wide Azimuth OBC data, particularly fault imaging which is sensitive to velocity accuracy. Fault imaging can be smeared and fault shadows can be observed within complex strike-slip fault systems if the azimuthal dependency of wave propagation is not properly honored. In this paper, we will present an orthorhombic model building flow and demonstrate with the Luda OBC data that our approach can successfully reconcile the structural discrepancies between seismic images from different azimuths and provide a clear and sharp fault image with the WAZ stacking process. Figure 1: Wide azimugth orthogonal patch pattern used in Luda OBC acquistion (a) and offset-azimuth-fold plot for one patch (b): Radius of the diagram represents offset which is up to 10000m and each color-coded cell represents fold within a sector 10° x 500m.