Mapping irregularly spaced data
Figure 10.9a is the result of map-migrating Figure 10.9b, which shows the lines of seismic control marked by diagonal dashes. The map shows a high on a north plunging, anticlinal nose. What additional program would you recommend to check weaknesses in the interpretation before recommending a well to test for hydrocarbon accumulation?
In map migration, observed traveltimes to a reflector are mapped along seismic lines and contoured. The contoured surface is then gridded into bins, each bin is migrated, and the result is contoured to yield the migrated map. Migration is discussed further in problem 9.27 (see also Sheriff and Geldart, 1995, section 9.12 for more details).
Figure 10.9b shows that there is relatively little control on the structure except on the east flank, so appreciable additional seismic work is required before a well location can be selected.
Most of the seismic lines in Figure 10.9a, except for those on the east flank apparently show little structural dip, so the structural picture must be inferred from jump correlations between seismic lines. Jump correlation is highly suspect as faults or dip can also explain the situation even if the correlations are reliable.
In particular, there is little evidence of south dip except that inferred from correlation between disconnected seismic lines. Consequently, a N25E line connecting the two mapped high closures is called for and it should extend far enough north to confirm north dip as well as south dip. There is little control directly over the central high, and the absence of mapped faults in this region may be a consequence of this poor control. At least one east-west line across the high is required. Based on the results of these two lines, additional lines will probably be required.
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Also in this chapter
- Improvement due to amplitude preservation
- Deducing fault geometry from well data
- Structural style
- Mapping faults using a grid of lines
- Fault and stratigraphic interpretation
- Interpretation of salt uplift
- Determining the nature of flow structures
- Mapping irregularly spaced data
- Evidences of thickening and thinning
- Recognition of a reef
- Seismic sequence boundaries
- Effect of horizontal velocity gradient
- Stratigraphic interpretation book
- Interpretation of a depth-migrated section
- Hydrocarbon indicators
- Waveshapes as hydrocarbon accumulation thickens