| Program | KNGMG kring Noord december lezing heeft als onderwerp:
“Broadband Seismic & the importance of shape and bandwidth of the seismic spectrum” en wordt gepresenteerd door Dr. Hans Dankbaar.
- Time: Tuesday 4 December 2018, 17:00-18:00. You are welcome from 16:30 onwards. Drinks and some snacks will be available.
- Place: NAM office, Room 2J.04 (the “Yellow Room”).
Abstract:
In 2011, CGGV was the first acquisition company to introduce a novel marine acquisition technology called ‘BroadSeis’™, which claimed to provide seismic data with a significantly increased bandwidth, some 2-100 Hz. Conventional data have a bandwidth of about 8-60 Hz. Key characteristic of their new method was that the hydrophone cable was towed in a slanted-curved shape behind the boat, with depth varying from 5 – 60m. ‘Broadseis’ indeed appeared to provide a step-improvement in data quality -Shell was one of the first companies to buy and evaluate their spec data. Soon thereafter, other acquisition companies came with (sometimes similar) methods that made similar claims. Nowadays, broadband seismic has nearly become the standard for marine acquisition – wherever application is possible – and also broadband methods for onshore acquisition have been developed.
Broadband seismic data have much improved characteristics of the seismic wavelet. The advantages are: more stable and faster interpretation, better imaging & interpretation in poor-data areas, resolving thick layers (& their properties), higher vertical resolution (less tuning), and less weather-downtime ($$) during acquisition.
The benefit of an increased bandwidth to the high end of the spectrum (up to 100 Hz) is restricted to shallow levels (about 1 sec below seafloor). The main advantage is the increased bandwidth to the low end, where it has to be noted that adding the 4 to 8 Hz, and 2 to 4 Hz, each time adds one octave to the spectrum – which is very significant. The increased awareness of the value of low frequencies for the appearance and interpretability of seismic data, also triggered investigation of the spectral content of existing (conventional) data. They often appeared to have a far from optimal spectrum, and new workflows for ‘broadband’ (re-)processing of conventional data were developed, with special focus on spectral shaping methods.
In this presentation I will elaborate on the above and show many examples.
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