Reflection waveform inversion based on cross-correlation misfit function

On a velocity and density model, the density from conventional FWI (Full Waveform Inversion) is seriously migrated, namely low wavenumber information in the model hasn't been recovered. Since RWI (Reflection Waveform Inversion) can estimate low wavenumber component, the combination of RWI and FWI can invert the density model more accurately. A velocity-density RWI model based on crosscorrelation-based misfit function is proposed. This paper first reviews the two-parameter inversion based on the conventional acoustic wave equation, and analyze the migration characteristics of density inversion using a radiation mode; then synchronously updates velocity and density by the Gardner formula based on the high trade-off between velocity density model when running RWI, and input the RWI results as the initial model for traditional velocity-density FWI; and finally builds a velocity-density RWI+FWI inversion workflow. Application on a simple two-layer model and a resampled Sigsbee 2A model has proved that RWI could avoid inversion to be trapped in local minima and suppress density migration; and in the process of RWI, low wavenumber information of velocity and density could be accurately recovered by using the Gardner formula to update velocity and density at the same time. © 2020, Editorial Department OIL GEOPHYSICAL PROSPECTING. All right reserved.