Blended Source/Nodal Ocean Bottom Seismic Acquisition

Ocean bottom seismic (OBS) data have been used for appraisal and development applications for a number of years in the North Sea, West Africa, Gulf of Mexico, and more recently offshore Brazil and SE Asia but the scale of the surveys, by dint of their focus on field specific imaging, has been limited compared to towed streamer surveys in both size and duration. One of the challenges set by the oil companies has been to reduce the unit costs of OBS data – “If only the square kilometer rates were lower we would shoot more data” is a common mantra. The difficulty in doing this has been the inherent technical downtime experienced by all the contractors operating ocean bottom systems – the terminations, connectors, power distribution and data telemetry components within a traditional ocean bottom cable (OBC) system are inherently prone to failure due to the intrinsic nature of the cable deployment/recovery cycle where the cables are stressed and de-stressed every time they are laid onto/recovered from the seabed. It is akin to recovering the full streamer spread every line change for towed streamer operations. The desire to improve operational performance was the driving force behind the development of the Z700 autonomous nodal system and its extreme reliability has allowed ever larger seafloor spreads to be operated which has multiple benefits.