Time-lapse elastic full waveform inversion of CO₂ injection at CaMI FRS using VSP: a feasibility study

Ninoska Amundaray, Kristopher A. Innanen

Full waveform inversion (FWI) relies on the quality and frequency content of the data to recover subsurface models. Successful applications have proven to delimit reservoirs with high-resolution models, as well as, measuring parameter variations associated to production processes. Currently, an injection program of carbon dioxide (CO2) is being conducted at the Containment and Monitoring Institute Field Research Station (CaMI.FRS). Field data from the baseline phase has been successfully inverted for the site, and data from an advanced injection stage is expected to be recorded in the following years. Hence, there is a need to assess the extents and limitations of this technique to resolve changes in the reservoir through experiments designs consistent with settings deployed at CaMI.FRS. In this study, we examine FWI using vertical seismic profiles (VSP) with velocity-density and impedance-velocity parameterizations, and by two inversion strategies in the data-space for three stages of CO2 injection. Inverted models demonstrate superior constraints of P- and S-wave variations by a sequential inversion scheme in terms of relative change between modeled stages and model misfit. Likewise, impedance-velocity is suggested as the optimal parameterization to resolve reservoir changes with approximately 2% to 4% more measured variations.