3-D poststack datuming
|Series||Investigations in Geophysics|
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As a byproduct of 3-D migration algorithms based on wavefield extrapolation, 3-D stacked data can be datumed from the surface to a specified depth or time level in a 3-D sense. This capability can be particularly useful in reservoir studies. Basically, the surface wavefield is downward continued to a desired depth without invoking the imaging principle along the way. Figure 8.4-15 shows the 3-D zero-offset data (Figure 8.4-2) datumed from the surface z = 0 to a 1000-m depth. The following conclusions can be made:
- Since there are no sideswipes on the center line, I-241, datuming in a 2-D or 3-D sense is identical.
- However, there is a significant difference between 2-D datuming and 3-D datuming for lines with sideswipe energy — those that are increasingly farther from the center line, say, Line I-181.
The wave-equation datuming described here takes the input wavefield from one flat constant horizontal datum to another. Prestack and poststack wave-equation datuming using arbitrary 2-D datum interfaces is discussed in layer replacement. The constant datum level should not be a limitation, particularly in reservoir studies. For example, the 3-D stacked data can be datumed to the top of the reservoir level followed by detailed imaging of the target zone only.
Figure 8.4-15 Three-dimensional wave-equation datuming (left column) versus 2-D wave-equation datuming (right column) from the surface down to a 1000-m depth of the synthetic data shown in Figure 8.4-2.
- 3-D poststack depth migration
- 3-D poststack time versus depth migration
- Two-pass versus one-pass 3-D poststack depth migration
- Implicit versus explicit 3-D poststack depth migration