GeoStreamer

Mitigating the Effect of the Receiver Ghost

Collocated groups of hydrophone pressure sensors and vertical velocity sensors record the continuous interference between the wavefield scattered upward from the subsurface geology and the downgoing wavefield that carries the imprint of the reflecting sea surface, which varies with each shot. This downgoing component is known as the ghost wavefield.

Wavefield separation is a critical step in broadband seismic imaging workflows applied to multisensor streamer and node seismic data. The pressure and velocity sensors record each upgoing seismic event with equal polarity, while the time-delayed downgoing event (i.e., the ghost) is recorded with opposite polarity. This polarity difference enables effective separation of the two wavefields.

All events associated with sea-surface ghost reflections can be isolated and removed to support traditional high-resolution imaging and subsurface characterization. Alternatively, the separated wavefields can be used for SWIM (Seismic While Imaging with Multiples) to enhance resolution in the shallow subsurface, particularly in areas where conventional imaging methods are less effective.

The TGS wavefield separation solution preserves all pre-stack amplitude-versus-angle (AVA) information essential for accurate subsurface characterization. This is achieved by accounting for 3D emergence angle variations along each GeoStreamer.

From an operational standpoint, multisensor streamers are inherently quieter, as they allow for deep towing with a shallower front end. This configuration reduces mechanical tension and enables very wide streamer spreads. Deep towing also delivers a rich low-frequency response in the upgoing wavefield, while the design preserves high-frequency content. The result is a broadband signal that is not affected by sea-surface variations.

Accurately removing the time- and space-varying downgoing wavefield, known as the receiver ghost, improves survey repeatability, which is critical for 4D reservoir monitoring and CCS/CCUS applications.

eBirds Enable Control of Receiver Positions

Tri-wing eBirds, integrated in the GeoStreamer, enable depth and lateral steering control with minimal drag. Safety is improved, positioning is more accurate, and reservoir monitoring is more repeatable.

Streamer fanning can minimize infill during acquisition. Other benefits include improved safety during deployment, retrieval, and in-sea maintenance.

This Kongsberg eBird is specially designed for the GeoStreamer and offers effective lateral steering and depth control of seismic streamers with a minimum of additional acoustic noise. This uniform three-wing solution and the built-in controller also provide full roll control capabilities, with eBirds mounted every 300 m along the streamers. Feather correction achievable is typically two to three degrees.