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GCPhase Residules Can Reveal Stratigraphic Features*
Oswaldo Davogustto1
Search and Discovery Article #41141 (2013)
Posted June 30, 2013
*Adapted from the Geophysical Corner column, prepared by the author, in AAPG Explorer, April, 2013, and entitled “It’s Just a Phase (Residue)”.
Editor of Geophysical Corner is Satinder Chopra ([email protected]). Managing Editor of AAPG Explorer is Vern Stefanic
1University of Oklahoma, Norman, Oklahoma ([email protected])
In the March AAPG Explorer Geophysical Corner (Search and Discovery Article #41140) my colleagues Marcilio Matos and AAPG member Kurt Marfurt discussed the concept of phase unwrapping and the computation of phase residues. Here, we go deeper: I elaborate on the application of phase residues to seismic
data – and the resulting subsequent interpretation of geological features.
Some geologically induced spatial discontinuities, such as channels and faults, easily can be identified as seismic
phase shifts or amplitude anomalies when they are above
seismic
resolution – but phase shifts from condensed
sections
and erosional unconformities can be subtle and not as easily detected. Spectral decomposition is a proven, powerful means of
identifying
such discontinuities at specific frequencies that are otherwise buried in the
seismic
broadband response.
Although seismic
acquisition and processing preserve
seismic
phase very well, little has been published about interpreting the phase components resulting from spectral decomposition. Morlet complex wavelet transform phase residues can improve
seismic
spectral decomposition interpretation by detecting the phase discontinuities in the joint time-frequency spectral phase component – by evaluating the phase shifts that are derived from thickness changes in a wedge model.
We unwrap phase the phase traversing a rectangular contour about each time-frequency sample. In almost all incidents, the contour closes. However, in some cases we have a +180 or -180 degree phase anomaly. We display the location of these phase residue anomalies and correlate them to stratigraphic discontinuities and inconsistencies in seismic
data quality.
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We are able to map interference patterns between the wavelets that occur below
Based on the response of the phase residues and the tops interpreted from the logs, we identified the incision stages in the phase residues attribute. We interpreted each stage as a
Figure 1 shows our well-to-
In Figure 2 we display the
In Figure 3 we show a chair diagram of the In conclusion, we demonstrated how the use of phase residues can be effectively applied to reveal and enhance important stratigraphic features not otherwise revealed by conventional I would like to thank Mark Falk and Al Warner for their support and advice in this project. I also would like to thank Chesapeake Energy Corporation and CGG-Veritas for donating the data for this project, and to Schlumberger and CGGVeritas for facilitating the software used in these displays. |