A robust imaging workflow to take advantage of long-offset broadband data acquisition

Abstract

In the past decade, marine seismic acquisition has evolved from narrow-azimuth (NAZ) to wide-azimuth (WAZ) geometries toward the latest offering of long-offset full-azimuth (FAZ) surveys with slanted cables. This broadband long-offset acquisition design is driven mainly by the demands of improved illumination in complex areas such as Gulf of Mexico (GOM) subsalt environments. Two-way wave-equation algorithms, such as reverse time migration (RTM) and full-waveform inversion (FWI), are required to optimally use these improved data. Their high-fidelity nature enables them to honor complex velocity fields with the accuracy required, particularly for migrating long-offset data and, as a result, for producing satisfactory model refinements and images when other methods fail. To achieve image improvements, an efficient workflow has to be established to maximize the power of broadband long-offset acquisition by applying velocity model building with FWI, imaging with RTM compensation for ghost effects in both steps, and outputting partial images for further image optimization. With the best acquisition and imaging algorithms, RTM images can be improved further by postimaging enhancements using vector image partitions (VIP) in the GOM.