Q Tomography

Spatial variations in the absorption properties of the overburden cause frequency-dependent dissipation effects. This results in seismic amplitude attenuation and wavelet phase distortion which masks underlying events and decreases resolution.

CGG's proprietary Q tomography and Q PSDM help address these issues. Q tomography builds a model of the anomaly using pre-stack amplitudes. Q PSDM can then use this model to compensate, recovering bandwidth, allowing meaningful AVO studies to be performed and aiding in the accurate prediction of reservoir properties.

Frequency Shift Q Tomography (FS-QTOMO) is a refinement of the method. It's a purely data driven method using centroid frequency shift information from surface seismic data for back-propagation along ray paths to reconstruct the attenuation distribution in terms of Q (Quality Factor) values.

Features

  • Implemented for Kirchhoff, Beam and RTM algorithms
  • Compensates for frequency-dependent loss during propagation, giving correct
    • phase
    • amplitude
    • resolution
  • Uses the estimated absorption model from frequency-dependent Q tomography to compensate for Q effects relative to the background
  • Goes beyond simplistic surface-consistent assumptions to compensate for transmission effects anywhere in the overburden.

Benefits

  • Enables meaningful AVO analysis under complex overburdens, for example:
    • gas pockets or gas hydrates
    • unconformities
  • More accurate prediction of reservoir properties
  • Easier identification and interpretation of deeper reflectors

 

Without Q PSDM With Q PSDM

Slide to compare

These sections from our Barreirinhas Basin multi-client survey, offshore Brazil, compare conventional PSDM overlain by our tomographic Q model (left) with results obtained with Q PSDM using that Q model (right).

Automatic Gas Pockets Detection by High-resol...

Fatiha Gamar | Patrice Guillaume | Antonio Pica | Geoffroy P...
©2015 EAGE

Image quality enhancement using volumetric Q-...

Fatiha Gamar | Loic Janot | Diego Carotti | Jenny Morante Go...
©2016 EAGE

Imaging through mega gas clouds in offshore B...

Nina Lin | Xiaodong Wu | Yi Xie | Joe Zhou | Suni Sulaiman |...
©2016 EAGE
Subsurface Imaging - RTM

Reverse Time Migration

Create accurate seismic images in the most complex of geological environments.

Subsurface Imaging - FWI

Full Waveform Inversion

Reveal intricate velocity details for the clearest images. Harness seismic low frequencies from BroadSeis, StagSeis, seabed and land data.

Multi-Client Data - Brazil Barreirinhas Basin

Brazil - Barreirinhas Basin

The Megabar survey in the Equatorial Margins of Brazil provides over 14,000km2 of BroadSeis data with advanced pre-stack depth migration
EAGE YouTube - Q-Tomo

EAGE YouTube Channel

E-Lecture
Automatic Gas Pockets Detection by High Resolution Volumetric Q-Tomography...
by Fatiha Gamar
© 2017 EAGE Education B.V.
Subsurface Imaging

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