Shallow Near-Surface Features

Accurate model building with reflection tomography is tricky in shallow water environments. Data diversity is poor and short wavelength, near-surface, velocity contrasts can break the high-frequency assumptions of ray-tracing methods.

The first example shows a shallow water application of FWI.  It resolves near-surface features and reduces seismic imaging uncertainty in an area with complex overburden heterogeneities. Unresolved, small, near-surface channels and gas impact the image quality. The velocity varies on a short wavelength and there is a lack of data. As a result, models built with reflection tomography cannot capture the detail required to resolve the imaging challenges that impact the overburden and shallow targets. 

The PGS FWI model resolves the complex velocity variations, removing the imprint of a complex overburden channel system that impacted the accurate volumetric measurements at the target interval. 

Co-rendered FWI model on seismic data with extracted velocities shown in one channel system. Slide the bar to compare two images. The image on the left, without FWI, shows the channel imprint on extracted amplitudes below the channel. In the image on the right this imprint has been removed using the FWI model.