Low Frequencies Unlock Visco-Acoustic Full Waveform Inversion Capability in Trinidad

A large Ocean Bottom Node (OBN) survey acquired off the east coast of Trinidad has allowed Shell the opportunity to deploy another application of its visco-acoustic Full Waveform Inversion. The setting is ideal, with pervasive shallow gas covering the area resulting in dispersion and attenuation. A proper and accurate earth model including the Q anomalies in this area is more accurately determined with visco-acoustic FWI over tomographic methods given shallow water depths resulting in incoherent shallow images and migrated gathers. In addition to the Q-field, the inversion will also derive the velocity field including the resulting slow-downs from these gas zones and ultimately improve image quality. The higher quality low frequencies recorded by the OBN has resulted in a more accurate and geologically reasonable model where previous Full Waveform Inversions using streamer data have left inaccuracies. And from this more accurate model, we present a substantial image uplift.