Paper submitted to EAGE Annual 2026
Summary
Source vessels involved in Ocean Bottom Node (OBN) data acquisition use airgun sources, which fire in a dithered manner to facilitate deblending of the data. The number of sources per vessel varies depending on the objective of the survey. For Development surveys with a 4D objective, one usually aims at avoiding self-blending in the reservoir zone. Sampling and free record length requirements then typically restrict the number of sources per vessel to two or three. For Exploration OBN surveys selfblending is traditionally considered less of an issue, as one typically aims at structural imaging. Nevertheless, the maximum number of sources per vessel involved in such surveys is four at the moment, because of the increasing difficulty of deblending with higher blending fold.
Encoded shooting, in which firing delays between sources are deterministic rather than random, may offer a way forward in terms of using more sources per vessel, provided we can demonstrate that data quality after decoding is on par or better than after deblending. In this paper we focus on the case of Exploration OBN surveys and compare dithered shooting with four airguns against encoded shooting with 6 airguns. The comparison is made on Signal to Noise Ratio (SNR) in the data domain, low frequency Reverse Time Migration (RTM) images and ultra-low frequency Full Waveform Inversion (FWI) velocity updates.