Perfect storm: Combining sparse node acquisition with full-waveform inversion

Abstract Full-waveform inversion (FWI), a data-driven optimization algorithm, is a widely used tool for earth model building in seismic imaging. However, results are still subject to inaccuracies of the initial model and a possibly suboptimal acquisition geometry, especially in salt basin and salt tectonic contexts. In 2019 and 2020, a sparse ocean-bottom node (OBN) acquisition was pursued. It started a new era of long-offset and low-frequency acquisition that unleashed the power of FWI, becoming a very effective combination to build spectacular velocity models in salt basins. The sparse node survey design was very promising, but the high-velocity interfaces of salt in the subsurface were still compromised by the limitations of acoustic wave propagation. Increased physics in FWI enables us to interrogate the power of elastic FWI (EFWI) versus acoustic FWI (AFWI). Here, we demonstrate the application of EFWI on a large scale to uncover the unimaginably complex geologic structure and the importance of low-frequency content of the acquisition, especially when the initial model cannot be built from the legacy streamer data.