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GCCurvature Computations Enhance Exploration*
Satinder Chopra1 and Kurt J. Marfurt2
Search and Discovery Article #40838 (2011)
Posted November 28, 2011
*Adapted from the Geophysical Corner column, prepared by the authors, in AAPG Explorer, November, 2011. Editor of Geophysical Corner is Bob A. Hardage ([email protected]). Managing Editor of AAPG Explorer is Vern Stefanic; Larry Nation is Communications Director.
1 Arcis Corp., Calgary, Canada ([email protected])
2 University of Oklahoma, Norman, Oklahoma
Curvature attributes have become popular with seismic
interpreters and have found their way into most commercial
seismic
interpretation software packages. Curvature estimates were introduced as computations performed on interpreted 2-D
seismic
surfaces, and 3-D computations based on volumetric estimates of inline and crossline dip soon followed.
A 3-D volume of curvature values is produced by estimating reflector dip and azimuth at each data sample in a seismic
volume. We denote the output of such calculations as structural curvature because the calculations are performed on time-based or depth-based
seismic
data that define the geometrical configurations of subsurface structure.
A second type of curvature attribute
can be calculated by using
seismic
reflection amplitudes rather than geometrical shapes of structure. When an interpreter creates a 3-D horizon through a
seismic
amplitude volume, inline and crossline derivatives of amplitude-magnitude variations can be calculated across this horizon.
Attributes that define the gradient behavior of reflection amplitude in X-Y space across a horizon are called amplitude curvature and are valuable for delineating the edges of bright spots, channels and other stratigraphic features that produce lateral variations in reflection magnitudes.
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In Figure 1a we show a schematic diagram of the magnitude of a hypothetical In a 3-D Short-wavelength curvature tends to delineate details showing intense, highly localized faulting. In contrast, long-wavelength curvature enhances subtle flexures on a scale of 100, 200 or more image traces that are difficult to see on conventional Figure 3 and Figure 4 compare long-wavelength and short-wavelength computations of most-positive and most-negative amplitude curvatures and structural curvatures. In Figure 3, note that for both long and short wavelengths, most-positive estimates of amplitude-curvature (Figures 3a and 3c) provide considerable detail, whereas most-positive structure-curvature displays (Figures 3b and 3d) show larger-scale features. The same physics occurs for estimates of most-negative curvature – amplitude curvature (Figures 4a and 4c) depicts fine detail, but structural curvature (Figures 4b and 4d) shows larger features. Amplitude curvature is not a better When We hope to extend the work shown here to generate rose diagrams of lineaments observed on amplitude-curvature maps and compare these with rose diagrams obtained from image logs. We thank Arcis Corporation for permission to show the data examples, as well as for the permission to publish this work.
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