Offshore staff
OSLO, Norway – PGS has issued an update on its new acquisition and processing solution eSeismic.
According to an article in the company’s internal magazine, this treats the wave fields on both the source and the receiver side as continuous and requires seismic data to be recorded continuously and the source signals to be emitted uninterrupted while moving.
To generate the source wavefield using existing equipment, individual airguns are triggered with short randomized time intervals in a near-continuous mode.
One of the main benefits, PGS says, is the reduced environmental impact of marine seismic sources. The peak sound pressure levels are lessened substantially by triggering one airgun at a time, compared to triggering many airguns in an array simultaneously as in conventional marine seismic sources.
Sound exposure levels are also reduced.
The field trial was conducted in mid-year offshore Brazil, demonstrating peak sound pressure levels around 20-22 dB lower for the proposed method compared with conventional methods.
In addition, sound exposure levels were 8-9 dB lower for eSeismic data.
Dense cross-line CMP spacing is achieved without compromising the acquisition efficiency, the company added. The 800-m (2,624-ft) wide sail line is sampled with 96 common mid-points compared to 32 with a standard dual-source configuration.
Another advantage is minimal vessel speed limitations as the technique does not require the seismic recording or sources to be triggered at specific spatial intervals. And limitations imposed by shot cycle time and record length can be relaxed.
11/16/2018
