Figure 7.5-11a shows a horizontal slab isolated from a 3-D poststack time-migrated volume of data. The objective is to isolate a bright spot located within the slab. First, remove opacity to obtain the image shown in Figure 7.5-11b. Note that the bright spot now can be easily detected. Next, label one voxel within the interior of the bright spot as if you are implanting a seed. Then, search for all neighboring voxels that represent amplitudes within a specified range of the seed amplitude. This process results in isolating a set of voxels that are contiguous in the form of a subvolume as highlighted in Figure 7.5-11c. The detected subvolume associated with the bright spot is displayed in this figure within the context of the surrounding depositional environment.
The seed detection can be repeated by adjusting the threshold amplitude associated with the seed voxel to produce a series of subvolumes with increasing size as shown in Figures 7.5-12a through f. It is evident that the case shown in Figure 7.5-12b best defines the size of the bright spot. The subvolume that represents the bright spot can be isolated completely from the entire image volume as shown in Figure 7.5-12g. By proper color coding of amplitudes within the subvolume, the potential hydrocarbon-bearing feature labeled as sweet sand can be identified. Also, observe the improvised structural contours around the sand body.
Seed detection can be used to interpret horizons with complex geometry without actually picking traveltimes. Based on a crude definition of the horizon geometry, a horizon-consistent time slab is extracted from the data volume used in interpretation. Figure 7.5-13a shows a color-coded time horizon associated with the top boundary of a karstic limestone layer interpreted from a time-migrated volume of data using the seed detection technique applied to the time slab. The same horizon in map view is shown Figure 7.5-13b.
Figure 7.5-12 (a) through (f): Subvolume detection to delineate the spatial extent of the bright spot identified as in Figure 7.5-15, and (g) amplitude manipulation to delineate the structural and stratigraphic features of the prospective sand body associated with the bright spot anomaly. See text for details. (Interpretation by Gerald Kidd; courtesy Paradigm Geophysical.)
- Interpretation of 3-D seismic data
- Time slices
- 3-D visualization
- Removal of opacity
- Structural interpretation
- Stratigraphic interpretation