eSeismic

Continuous Sources and Seismic Wavefield Recording for Reduced Sound

eSeismic was developed for areas where received sound levels must be very low for environmental reasons. This unique approach enables high-quality seismic data to be recorded with the lowest sound emissions of any source concept.

All data recorded for each sail line are processed as one record, require no shot deblending, and potentially offer very high-resolution seismic images where dense 3D shot sampling is relevant. eSeismic uses random triggering of individual source elements in space and time to create seismic wavefields with the properties of white noise.

Airgun sound pressure level (SPL) and sound exposure level (SEL) are the lowest for any marine source configuration. The eSeismic method is also applicable to towed marine vibrators.
As all source wavefield energy contributes to each output gather location, the deep signal penetration is comparable to traditional large energy sources, however, energy is spread over time to minimize emitted environmental sound levels.
Equally applicable to both shallow and deepwater settings, with an unrestricted target depth range.
Crossline spatial sampling may be improved by operating multiple sources simultaneously. While inline sampling may be improved by significantly denser sampling along all source lines.
Continuous sampling of emitted source wavefield over entire sail line, enabling multi-dimensional deconvolution of pre-stack gathers at any user-specified location or interval.
Not restricted to any model of airgun, and applicable to non-impulsive source concepts such as marine vibrators.
Vessel speed is less limited by shot cycle time and record length, so survey efficiency may be higher in appropriate settings.

Differentiating Features

Individual air guns are triggered randomly in both a spatial and temporal manner, and several air guns are typically triggered each second. As the emitted continuous seismic wavefield has properties approaching white noise, each of the emitted wavefields is uncorrelated.

In contrast to traditional airgun firing where deblending is required to separate consecutive shot gathers with overlapping data, with eSeismic all data recorded from each sail line are processed as one record. Common receiver gathers are recovered from a multi-dimensional deconvolution that involves no deblending and the gathers typically only have a 12.5 m interval. The final migrated seismic images are equivalent to the results from traditional imaging.

The image gather displays below compare several seconds of data recorded with traditional air-gun arrays with continuously triggered air-gun elements. The emitted source wavefield from each airgun is spatially symmetric and has the lowest-possible sound pressure level (SPL) and sound exposure level (SEL) of any air-gun source concept (see second figure below). The eSeismic method has also successfully been tested where the only active source was the natural acoustic wavefield generated by the vessel towing the GeoStreamer spread.

Peak sound pressure levels (in dB re 1 mPa) as a function of in-line and crossline distance in meters from the geometric center of the source at a depth of 10 m (4 m below the source depth) for a 4130 cubic-inch array (left), and when triggering individual airguns in a near-continuous fashion (right). Specific numbers will vary somewhat by survey, but SPL has been reduced by as much as 20-22 dB at 500 m from the source location (a 92% decrease), and SEL integrated over a 10.5 second window was reduced by 8-9 dB at 500 m from the source location (a 65% decrease); both by comparison to a conventional 4130 cubic inch array of airguns.

Continuous Sources and Seismic Wavefield Recording for Reduced Sound

Differentiating Features

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