Stratigraphic interpretation

Problems in Exploration Seismology and their Solutions

Series	Geophysical References Series
Title	Problems in Exploration Seismology and their Solutions
Author	Lloyd P. Geldart and Robert E. Sheriff
Chapter	10
Pages	367 - 414
DOI	http://dx.doi.org/10.1190/1.9781560801733
ISBN	ISBN 9781560801153
Store	SEG Online Store

Problem

Interpret the seismic section shown in Figure 10.15a.

Solution

The most striking feature of this section is probably the progradational pattern $AA'$ indicating a source to the right of the section. These prodelta reflections (seaward of a river delta) show both toplap and downlap terminations. Note that these prograding reflections are more continuous at the right and left sides of the section than in the region under the surface channel. There may also be a slight sag in reflections under the channel, and they suffer similar quality deterioration. An interpreter would not interpret these quality changes as having stratigraphic significance.

The thin wedge above $B$ that pinches out about midway on the section shows downlap from the left, suggesting a shift in the source of the sediments from the time when the deeper prodelta sediments were being deposited. Downlap is seen onto $DD'$ and reflections below $DD'$ truncate against this reflection; it is probably an unconformity and possibly a sequence boundary.

Figure 10.15a.  Seismic section (courtesy Chevron Oil Company).

Note the change in overall character at reflection $CC'$; it is known from well control that $CC'$ separates marine sediments below from nonmarine sediments above. However, the decrease in multiplicity on this CMP section as one goes shallower (because of the mute applied in processing) might also produce a character change.

Dip is gently to the left on this section so the right dip at and below $DD'$ constitutes a dip reversal that may have structural significance.

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Effect of horizontal velocity gradient	Interpretation of a depth-migrated section
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Data processing	Refraction methods
Table of Contents (book)

Also in this chapter

• Improvement due to amplitude preservation
• Deducing fault geometry from well data
• Structural style
• Faulting
• 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
• Unconformities
• Effect of horizontal velocity gradient
• Stratigraphic interpretation book
• Interpretation of a depth-migrated section
• Hydrocarbon indicators
• Waveshapes as hydrocarbon accumulation thickens

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