Elastic full-waveform inversion using OBN data acquisition

Full-waveform inversion (FWI) has been widely used on 3D datasets to build detailed velocity models over the past ten years. Most of these projects used pressure data and an acoustic approximation with the assumption that the field data is dominated with P waves. This approach of FWI can determine parameters related to the acoustic wave equation with a focus on updating the velocities through minimizing the misfit between the observed data and the model data. Acoustic FWI has shown tremendous potential, especially in 3D wide-offset acquisitions using the pressure component of the collected data and with simple geologies, including wide-azimuth streamer, ocean-bottom surveys and land types of geometries, where the advantage of FWI has convinced the oil industry to pursue the next step by involving more physical properties. The question however remains on how far we can properly describe the field data with the acoustic approximation, and at what point we need to switch over to a much more expensive elastic wave equation implementation. In a complicated geological region such as the Gulf of Mexico (GoM), the seismic wavefield can be complex and elastic FWI is probably needed to achieve a better velocity model, even when we use mostly the pressure data alone. In this paper, we demonstrate the application of elastic FWI on a sparse node OBN data from GoM and show comparisons to the acoustic solution.