Technology Editor, Subsea & Seismic
ROME –At the European Association of Geoscientists and Engineers annual convention and exhibition today, the potential benefits of conducting wide azimuth seismic acquisition by towing streamers in concentric circles rather than straight lines were outlined by Nick Moldoveanu of WesternGeco.
In his presentation, Moldoveanu said that circular geometry is efficient for towed-streamer wide angle azimuth surveys because only a single streamer vessel with a single source array is needed and also because acquisition is continuous.
WesternGeco modeled a parallel versus circular survey over one area, and Moldoveanu said the results were positive for the circular method with proper streamer steering, accurate receiver positioning, and advanced noise attenuation.
The simulation was for four parallel passes over 900 sq km (347 sq mi) using one streamer vessel and three source vessels compared to the circular geometry over the same area. The test indicated that the parallel acquisition would require 62 days with 160,000 shots while the concentric run should take 61 days for 321,706 shots. This larger number of shots in the circular run plus the higher fold and wider range of azimuths worked in its favor.
A Gulf of Mexico feasibility test also was run to test the ability to make circular runs. One vessel with one source array and 10 steerable streamers 7,000 m (4.35 mi) long with 120-m (394-ft) separation were used. The test proved it was possible to sail in circles while maintaining constant streamer separation. Data acquired also was processed to confirm that could be completed successfully, too.