Paper Summary
Depth imaging in complex geology requires an accurate background model. In this case study, over the Clair field, we make use of high density node data set and Full Waveform Inversion (FWI) with Inverse Scattering Imaging Condition and Vector Reflectivity to solve the low wavenumbers in the model. The purpose of FWI was to capture the hard and fast seafloor followed by a strong velocity inversion, numerous localized high velocity bodies and accumulations of gas in the overburden, as well as mapping the rotated fault blocks in the target interval below Base Cretaceous Unconformity. The inversion was done with a wavelet estimated from the data, to avoid possible bias in model updates related to phase errors in the deterministic wavelet. After solving the background model, the inversion continued up to 60 Hz. The final FWI model provided a well focused image with realistic structures and a flatter gas-oil contact than the vintage model. Significant amount of details have been captured in the FWI model, which correlates well to sonic data and the geological knowledge of the area.