Abstract

Conventional method of seismic data analyses provide high-quality seismic image, but the image remains qualitative. Elastic full waveform inversion can provide quantitative measure of elastic parameters, which can be used to quantify the lithology, fluid and gas content, and excess pressure. Both travel-time and amplitude information within shot domain data are used to invert for the sub-surface velocity, from a starting model containing the long wavelength features. Although full waveform inversion is computationally intense, the ability to invert for both P- and S-wave velocity, in a data driven manner, makes the computational burden worthwhile. Over the last ten years, we have developed a suite of full waveform inversion algorithm and have applied to multi-component ocean bottom cable data from the North Sea to quantify gas clouds, walk-away VSP data from the Gulf of Mexico to determine the presence over-pressure beneath a salt dome, and to quantify sequestrated CO2 in he time-lapse mode. We demonstrate that the waveform inversion can indeed provide P and S-wave velocities on metric-scale and can quantify thin layers of gas or CO2, over pressure region etc, and should be used prior to expensive drilling.