Toward a closed loop from seismic imaging to earth-model building

Abstract

Velocity-model building is the first task of seismic inversion and the foundation of the subsequent data-processing workflow. When the earth velocity becomes multivalued with respect to the propagating direction of the waves, velocity-model building becomes severely underdetermined and nonunique. The traditional workflow separates velocity-model building from lithologic inversion, which hampers both processing steps. An integrated model-building scheme is demonstrated to simultaneously consider prestack seismic data and its structural and lithologic inversion results from a previous iteration. The prestack seismic inversion is performed using wave-equation migration velocity analysis (WEMVA) for vertical transverse isotropic (VTI) models. To constrain the seismic inversion, the geologic information is integrated as spatial-model correlations, and the rock-physics information as lithologic-model correlations. This feedback step completes the loop from seismic imaging to lithologic-model building, where previous rock-physics estimations and geologic interpretations can be validated further and updated in order to constrain the next WEMVA iteration. Improvements from the integrated inversion scheme are shown on a Gulf of Mexico field data set.