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Curvature Attributes & Applications1. Preconditioning of dataStructure-oriented fi lteringSeismic data are usually contaminated with noise and so need to be preconditioned with noise removal processes. Structure-oriented fi ltering is commonly used to address this.

Regularization through 5D interpolationNon-uniformity in the distribution of offsets and azimuths in seismic data creates artifacts such as acquisition footprint that mask the subsurface geologic features of interest. Problems arising from non-uniformity as well as missing data in seismic data volumes can be addressed with 5D interpolation.

Segment of an inline from (left) a 3D seismic volume, and (right) the same segment from the seismic volume with structure-oriented fi ltering run on it

Stratal slices 32 ms through coherence volumes computed from amplitude data (left) before, and (right) after 5D interpolation. Regularization of offset and azimuth information leads to better defi nition of features of interest.

2. Multi-spectral estimates of curvatureCurvature images having different wavelengths provide different perspectives of the same geology and so demonstrate the interpretational value of these attributes.

Stratal slices through (left) principal most-positive curvature (long-wavelength) volume computed from input seismic volume, (right) principal most-positive curvature (short wavelength) volume computed from input seismic volume after 5D interpolation.

Stratal slices through (left) principal most-negative curvature (long-wavelength) volume computed from input seismic volume, (right) principal most-negative curvature (short-wavelength) volume computed from input seismic volume after 5D interpolation.

3. Structural curvature vs. amplitude The conventional computation of curvature, termed structural curvature, entails the use of lateral second-order derivatives of the structural component of seismic time or depth of refl ection events to generate them. If the lateral second-order derivatives are applied on the amplitudes of seismic data along the refl ectors, then the attribute computation is termed amplitude curvature. Amplitude curvature furnishes more interpretational detail than structural curvature.

Principal most-positive curvature long-wavelength structural curvature

Principal most-positive curvature (long-wavelength) structural curvature

Principal most-positive curvature (long-wavelength) amplitude curvature

Principal most-positive curvature long-wavelength amplitude curvature

5. Curvature refl ector convergenceRefl ector convergence is a measure of the change in refl ector normal about a more or less horizontal axis and is useful in the interpretation of angular unconformities.

Case-1: where the deposition within the channel shows no signifi cant convergence.

Case-2: where the deposition within the channel is such that the west channel margin is converging towards the east. This is displayed in color to the far right with the help of a 2D color wheel.

Case-3: where the deposited sediments within the channel are not converging at the margings, but the levee/overbank deposits converge towards the channel (west deposits converge towards the east and vice-versa.)

Case-4: where both the strata within the channel and levee/overbank deposits are converging. This appears to be a combination of cases (b) and (c) as shown to the right.

Time slice at 1600 ms. The sediments indicated by magenta arrows are thinning towards the northeast. Refl ectors that are nearly parallel (low convergence magnitude) appear white and are rendered transparent

Cartoons demonstrating convergence within a channel with or without levee/overbank deposits

6. Curvature refl ector rotationRefl ector rotation is a measure of the change in refl ector normal about a more or less vertical axis and determines the rotation of fault blocks across discontinuities such as wrench faults.

Time slice at 1.190 x from coherence volume and vertical slices through seismic amplitude co-rendered with vector rotation. Red indicates down to the right across the fault, while blue indicates up to the right across the fault

7. Applications for unconventional reservoirsNatural fractures in shale formations can provide permeability pathways, so can be characterized with curvature attributes.

Chair display with seismic on the vertical and horizon slice from the k1 most-positive principal curvature. Notice the correlation of the difference lineaments on the curvature with their seismic signatures. Horizon slice at the Muskwa level (Horn River Basin) from the relative acoustic impedance

volume derived from thin-bed refl ectivity inversion of 3D seismic data. Overlaid on this display are the most-positive curvature lineaments with the use of transparency.

4. Euler curvatureEuler curvature is a generalization of the dip and strike components of curvature in any user-defi ned direction, and is useful for interpretation of lineament features in desired azimuthal directions. (indicated with double-headed arrows in circles)

For more information contact Satinder Chopra at Arcis Seismic Solutions, TGS, Calgary at 403.781.5851, schopra@arcis.com. www.arcis.com

© 2013 Arcis Seismic Solutions, TGS, Calgary, CanadaThis poster represents our current understanding about curvature attribute analysis. While we recommend its application to seismic data analysis, we accept no responsibility for its use. We appreciate your ongoing feedback and discussion. More details on curvature analysis can be found in the book entitled 3D Seismic Attributes for Prospect Identifi cation and Reservoir Characterization, (SEG Publication).

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