Volumetric Curvature Attributes for Mapping Faults, Fractures, Depositional and Diagenetic Features

Satinder Chopra¹ and Kurt J. Marfurt^2
1Arcis Corporation, Calgary, AB, Canada
²University of Oklahoma, Norman, OK

Curvature is a measure of the deviation of a surface from a plane. The more a surface is structurally flexed, folded, or faulted, the larger its curvature. Curvature is also sensitive to domes and sags associated with salt and shale diapirism, to differential compaction over heterogeneous sedimentary deposits, and to dissolution and collapse associated with diagenesis. Using well-established models of structural deformation coupled with well control, geoscientists can use curvature measures to predict paleostress and areas favorable to natural fractures. We demonstrate the application of curvature attributes for superior mapping of subsurface channels, levees, bars, contourites, and other stratigraphic features, particularly in older rocks that have undergone differential compaction.

Until recently, curvature has been usually computed from picked horizon surfaces interpreted on 3D surface seismic data volumes. A significant advancement in the area of curvature attributes has been the volumetric estimation of curvature which alleviates the need for picking horizons in regions through which no continuous surfaces exists. The values of volumetric attributes are two-fold. First, the images have a higher signal-to-noise ratio than horizon-based attributes. Second, not every geologic feature that we wish to interpret may fall along a horizon that can be interpreted.

The orientations of the fault/fracture lineaments interpreted on curvature displays can be combined in the form of rose diagrams, which in turn can be compared with similar diagrams obtained from image logs to gain confidence in calibration. While a direct prediction of open fractures may require a significant amount of calibration through the use of production, tracer, image logs or microseismic measurements, volumetric attribute analysis serves as a powerful aid in defining the structural framework.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas