oa Density estimation strategy in full waveform well-to-well tomography

Seismic full-waveform inversion (FWI) is a method developed for estimating velocity distribution in a medium in which seismic waves travel through. Seismic velocities are expressed by the combination of two elastic constants and density in a homogeneous elastic medium, but density is usually estimated using an empirical formula or is fixed to a constant value in practice. The majority of elastic FWI studies have ignored the influence of density that could be an important parameter. Inverting for three elastic parameters is difficult problem even in FWI for a homogeneous elastic medium when solving for velocities that are composed of the three parameters coupled with each other, and the coupling effects prevent one from the appropriate estimation of the elastic parameters. Since, density is the useful parameter for hydrocarbon characterization, we investigate the best strategy to estimate density structure and reveal the difficulty of the estimation of density structure. We conduct several numerical experiments to estimate density structure. Our inversion results and grid analysis of misfit function show that density is affected by other parameter in the inversion and sequential inversion procedure is the most suitable strategy to estimate density.