Designature & Deghosting

Accurate 3D Designature and Deghosting for High-Fidelity Broadband Processing

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PGS offers a robust source designature workflow to design the optimal designature filter from various representations of the far-field signature from each shot. Shot-to-shot variations are derived from near-field hydrophone (NFH) recordings.
  • Designature compensates for shot-to-shot variations in the emitted wavefield from each shot, including bubble reverberations
  • Designature preserves signal energy and achieves phase stationarity in a broadband manner across all frequencies
  • Designature corrects for source directivity in both the inline and crossline directions
  • Processing-based receiver and source deghosting methods for single-sensor data provide broadband pre-stack data fit for matching with multisensor datasets during 4D reservoir monitoring projects

3D directional designature compensates for directivity of the emitted source wavefield in both inline and crossline directions and ensures that residual bubble is fully attenuated. The methodology preserves phase over all frequencies.

As a complement to wavefield separation of multisensor GeoStreamer data, PGS offers processing-based deghosting solutions for single-sensor streamer recordings and conventional source arrays. Under simplifying assumptions about the shape and reflecting properties of the sea-surface, PGS uses a deghosting solution based on the wave-equation, where a forward operator is derived that describes how all seismic events that are reflected by the sea-surface will create a ghost. The processing-based receiver deghosting is known as RBO (receiver-base bandwidth optimization), and the processing-based source deghosting is known as SBO (source-base bandwidth optimization).

Flexible Far-Field Signature Derivation

The availability of an appropriate far-field signature is a traditional challenge to designature workflows. PGS can model accurate signatures using the Nucleus+ software, use near-field hydrophones recordings, or derive a hybrid far-field signature from both measured and modeled data. The workflow generates notional signatures for each individual gun, and then computes a hybrid far-field signature that can incorporate all 3D directivity effects.

Bandwidth-Preserving 3D Designature

The PGS designature process creates a vertical 1D designature filter using the bandwidth optimized signature solution (BOSS+) methodology, which matches the far-field signature to a desired zero phase wavelet. Key benefits of the PGS BOSS+ flow include the preservation of the full bandwidth as no predictive deconvolution is employed, and that the low frequencies of the signal are zero phased appropriately.

Accurate Processing-based Receiver and Source Deghosting

The figures below show the application of receiver and source deghosting to data acquired with a single sensor. The receiver depth was 15 m, leading to notches at around 0, 50, 100, 150 and 200 Hz. The source depth was 7 m, leading to notches at around 0 and 107 Hz.

Raw shot gather in t-x and f-k domain acquired with a streamer depth of 15m and a source depth of 7m. Orange arrows show the receiver notch and the blue arrow is the receiver ghost (white/black).

 

RBO shot gather in t-x and f-k domain. Receiver ghost has been suppressed. Orange arrows show the receiver notch is filled and the blue arrow shows the receiver ghost is suppressed.

 

RBO + SBO shot gather in t-x and f-k domain. Receiver and source ghosts have been suppressed. Blue arrow shows that the source ghost is suppressed.

 

Amplitude spectra extracted from the data. Note the successful retrieval of a linear trend in the spectrum obtained after source and receiver deghosting (RBO + SBO orange line), light blue is hydrophone and dark blue is RBO.

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