Sim-source for 4D: Learnings from processing the first ISS OBN monitor survey at Atlantis

Driven by the notion that blending noise may materially increase the background noise level and obscure the interpretation of weak time-lapse (4D) signals related to subtle reservoir changes, the industry has not yet seen any simultaneous-source (sim-source) surveys acquired for reservoir monitoring. Thus, whether sim-source acquisition is feasible for 4D remains a long-standing question. In 2019, BP took the step forward to acquire the first sim-source ocean bottom node (OBN) monitor survey at the Atlantis field in the Gulf of Mexico (GoM). With 4D-friendly deblending and matching of sources from different vessels, we were able to mitigate the challenges associated with the 2019 independent simultaneous source (ISS) OBN survey and obtain a similar level of 4D signal-to-noise ratio (S/N) and valuable 4D signals comparable to what we could achieve with conventional OBN data. Further, meaningful subsalt 4D signals were revealed for the first time in the areas with fairly poor illumination even with the 2019 ISS OBN survey, partly due to the larger reservoir changes from a longer production history and a more accurate velocity built from full-waveform inversion (FWI).