Guralp Systems announced the successful deployment of an array of ocean bottom nodes as part of a 3D active marine seismic survey offshore Australia. The nodes have extended the aperture of the streamer survey from 8km to 30 km.
Guralp, in conjunction with their Australian representatives at the Seismology Research Centre, have recently supplied an array of 20 ocean bottom seismic nodes to the Australian Geophysical Observing System (AGOS). Following a test in shallow water the nodes were deployed for 1 week over an oil field on the North West Australian margin in a water depth of 1100m within the area of a 3D marine seismic survey. Seismic signals from the survey were recorded to offsets in excess of 30 km and could have been recorded to even larger offsets, had the acquisition geometry allowed larger separations between sources and receivers.
Alexey Goncharov at Geoscience Australia commented, “This is a major extension of the recording aperture compared to 8 km long streamers used on that survey.”
The large offset data obtained can be used for:
o Deep penetrating velocity estimates from travel time tomography
o Full wave form inversion
o 2D wide-angle reflection seismic imaging
o Improved NMO-based velocity analyses
o Broadband imaging by recording low frequency spectrum (2Hz to 8 Hz)
o Analysis of converted seismic waves, anisotropy and estimates of rocks fluid saturation from
o 3-component data
The Guralp nodes acquire 3 component broadband seismic data from 0.03Hz to 100Hz plus hydrophone data, and can operate for up to 12 months in water depths up to 6000m. The nodes were easily deployed using the 21m vessel Capricorn Lady equipped with an A-frame at the stern. The nodes sink to the ocean floor and start recording automatically. Their deployed location is determined using an acoustic positioning system. On completion of the survey the nodes are commanded to return to the surface using an acoustic communication link on the vessel. Once at the surface the nodes broadcast their position over radio to facilitate recovery.