Simultaneous Long Offset (SLO) – A Case Study in Long Offset GeoStreamer Seismic Acquisition & Processing
R.G. van Borselen BV, A.S. Long, E. von Abendorff, M. Purves and J. Norris BV
Event name: 6th EAGE Saint Petersburg International Conference and Exhibition
Session: Seismic Exploration Technology
Publication date: 07 April 2014
Info: Extended abstract, PDF ( 2.06Mb )
Price: € 20
An innovative 3D towed streamer project in offshore Gabon used a dual-vessel continuous long offset streamer configuration to acquire 0-12 km offsets with ten dual-sensor streamers. Streamer control for the 6 km streamers was robust and avoided operational complications or logistical penalties. In simultaneous acquisition, data can be recorded with a temporal overlap between two (or more) simultaneously fired shots. Using random dithered time delays when firing the sources ensures that in certain domains coherency-based methods can be utilized to separate the simultaneously recorded data. Simultaneous shooting maximized inline shot density for long record lengths, thus capturing unaliased deep target reflections from rugose base-salt and sub-salt horizons. Survey design benefited from prior 2D survey experiences with a variety of broadband source and streamer technologies, and the use of 2D streamers as long as 12 km. 3D illumination modelling further suggested that offsets as long as 16 km could be expected to yield useful base-salt and sub-salt reflections. Wavefield separation processing yielded full receiver-side deghosting onboard, followed by an inversion-based separation of simultaneous shots onshore. The ultra-long 12 km offsets combined with strong amplitudes of deghosted low frequencies have yielded encouraging sub-salt and pre-salt imaging.