Time-lapse joint full waveform inversion of diving and reflected waves

Full waveform inversion (FWI) can be applied to time-lapse (4D) seismic data for subsurface reservoir monitoring. However, it mainly relies on far-offset diving waves to estimate large-scale (low-wavenumber) variations of velocity structures, and thus may not penetrate deeper reservoirs. Alternatively, joint full waveform inversion (JFWI) assumes a scale separation in the model space such that low wavenumbers can be recovered from both diving and reflected waves, in addition to high-wavenumber reflection impedance perturbations. In this work, we apply JFWI to 4D data to improve the estimation of 4D velocity changes. A realistic synthetic study shows that a workflow of 4D JFWI followed by 4D FWI leads to an improved data fit as well as a more accurate estimate and better resolution of velocity changes than classical 4D FWI methods, in a reservoir zone that is not penetrated by diving waves due to limited source-receiver offset apertures.