Multi-Spectral Volumetric Curvature Adding Value to 3-D Seismic Data Interpretation
Volume attribute applications on 3D seismic data have recently been demonstrated for the prediction of fractures and other stratigraphic features. Geologic structures often exhibit curvature of different wavelengths. Curvature images having different wavelengths provide different perspectives of the same geology. Tight (short-wavelength) curvature often delineates details within intense, highly localized fracture systems. Broad (long wavelength) curvature often enhances subtle flexures on the scale of 100-200 traces that are difficult to see in conventional seismic, but are often correlated to fracture zones that are below seismic resolution, as well as to collapse features and diagenetic alterations that result in broader bowls. Such multi-spectral volumetric estimates of curvature are very useful for seismic interpreters and will be the focus of this presentation.
A fractional derivative approach for volume computation of multispectral estimates of curvature will be demonstrated. An important feature of this computation is the use of a fractional real number (α) whose value typically ranges between 1 (giving the first derivative) and 0 (giving the Hilbert transform) of the dip. The space domain operators corresponding to different values of α mentioned are convolved with the previously computed dip components estimated at every sample and trace within the seismic volume. Lower values of α decrease the contribution of the high frequencies, thereby shifting the bandwidth towards longer wavelength. Thus full 3D curvature attribute volumes are available for analysis at different scales, which helps extract meaningful and subtle information from seismic data.
Multispectral volumetric curvature attributes are valuable for prediction of fracture lineaments in deformed strata. Several applications of volume curvature have been completed in different geological settings, which are found to be useful for different stratigraphic features, ranging from imaging of channel boundaries, small scale faults to highly fractured zones.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009