|KGS Open-file Report 2002-49|
Example--"D" Sand, Sooner Unit, Colorado
ObjectivesDetermine "D" sand thickness between well control points.
Identify faults/discontinuities which could be barriers to fluid flow in the reservoir.
Sooner 3-D seismic surveyBlack horizons delineate seismic reflections corresponding to the top and bottom of the "D" sand. Over most of the 3-D survey area, the "D" sand is below seismic resolution (a "thin bed"). Below seismic resolution, reflections from the top and bottom of the sand maintain a constant temporal separation, which is unrelated to the true sand thickness. Envelope, frequency, and spectral decomposition attributes, which have been used elsewhere to estimate bed thickness, will be examined as potential predictors of "D" sand thickness
Figure 8. Vertical Seismic Section.
The envelope attribute has been calculated for the entire Sooner seismic data volume. A cross-sectional slice through the envelope volume gives a 2-D view of how this attribute varies in time. 3-D visualization can be used to display the spatial distribution of high envelope amplitudes (blue).
Figure 9. Cross-sectional view and 3-D visualization.
A map view shows how the envelope attribute varies laterally along the horizon corresponding to the top of "D" sand. This view is used to identify spatial patterns in the envelope amplitude which may correspond to changes in sand thickness. In general, higher envelope amplitudes correspond to thicker sands.
Figure 14. Crossplots of attribute versus "D" sand thickness.
Instantaneous phase and coherence, extracted along the "D" sand horizon, are examined for discontinuities/faults which may indicate reservoir flow boundaries.
Sooner 3-D SummaryThe 29 Hz Spectral Decomposition slice is the best single attribute for predicting "D" sand thickness.
A set of linear discontinuities in the northern part of the Sooner 3-D survey is best imaged on the Coherence map. These discontinuities may be faults, and are potential reservoir flow boundaries.
ConclusionsAttributes reveal information which is not readily apparent in the raw seismic data
Dozens of seismic attributes can be calculated using a variety of software packages
Attributes may be interpreted singly or using multi-attribute analysis tools
Different attributes reflect different physical properties of the underlying rock system
AcknowledgmentsAccess to The KINGDOM Suite software and the Sooner 3-D seismic data set was provided by Seismic Micro-Technology, Inc.
Suggested ReadingsBahorich, M. S., and S. L. Farmer, 1995, 3-D seismic coherency for faults and stratigraphic features: The Leading Edge, v. 14, p. 1053-1058.
Bodine, J. H., 1986, Waveform analysis with seismic attributes, Oil & Gas Journal, v. 84, June 9, p. 59-63.
Gersztenkorn, A., and K. J. Marfurt, 1999, Eigenstructure based coherence computations as an aid to 3-D structural and stratigraphic mapping: Geophysics, v. 64, p. 1468-1479.
Marfurt, K. J., R. L. Kirlin, S. L. Farmer, and M. S. Bahorich, 1998, 3-D seismic attributes using a running window semblance-based algorithm: Geophysics, v. 63, p. 1150-1165.
Marfurt, K. J., and R. L. Kirlin, 2001, Narrow-band spectral analysis and thin-bed tuning: Geophysics, v. 66, p. 1274-1283.
Nissen, S. E., 2000, Interpretive aspects of seismic coherence and related multi-trace attributes, Kansas Geological Survey Open File Report 2000-84: Available Online
Partyka, G., 2001, Seismic thickness estimation: three approaches, pros and cons, 71st Ann. Internat. Mtg: Soc. of Expl. Geophys., p. 503-506.
Partyka, G., J. Gridley, and J. Lopez, 1999, Interpretational applications of spectral decomposition in reservoir characterization: The Leading Edge, v. 18, p. 353-360.
Sippel, M. A., R. W. Pritchett, and B. A. Hardage, 1996, Integrated reservoir management to maximize oil recovery from a fluvial-estuarine reservoir: A case study of the Sooner Unit, Colorado, in Johnson, K. S. (ed.), Deltaic Reservoirs in the Southern Midcontinent, 1993 symposium: Oklahoma Geological Survey Circular 98, p. 288-292.
Taner, M. T., F. Koehler, and R. E. Sheriff, 1979, Complex seismic trace analysis: Geophysics, v. 44, p. 1041-1063.
Taner, M. T., 2000, Attributes revisited: Available Online
Kansas Geological Survey
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Updated Nov. 25, 2002
URL = http://www.kgs.ku.edu/PRS/publication/2002/ofr49/page2.html