Application of 3D Full Waveform Inversion to a synchronized, multi-level source dataset

Summary The development of a broadband acquisition system that records the low frequencies necessary for Full Waveform Inversion (FWI), without compromising the high frequencies desired in imaging, is a significant step forward. It is based on a multi-level synchronized source with the free-surface acting as part of that system in order to attenuate the source ghost. This proves to be a challenge for the FWI modeling engine which must generate an identical wavefield containing the receiver ghost and waterlayer multiples but without modeling a shot ghost which is absent in the acquired data. The seismic signature of any airgun array can be considered as the sum of independent point source signals corresponding to each gun called notional sources. We propose a methodology based on the decomposition of the multi-level source into notional sources, where each notional source is derived from the near field hydrophone records, to reproduce the recorded wavefield. For the first time the application of 3D FWI to a multi-level synchronized source data set, acquired over the Utsira High area in the North Sea, is presented with this novel approach. The FWI output reveals various meaningful geological structures such as shallow channels in the near surface and a shale diapir.