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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract:
Seismic
Modeling
:
Geological Predictions and Pitfalls
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Migrated End_of_Record - Last_Page 4---------------Seismic
sections across most geological structures are
distorted by sideswipe and/or lateral velocity changes in the
subsurface. Invariably, the distortion on the 20 migrated
section hides the features that are most desired. However,
through
seismic
models of similar geological structures, the
interpretational pitfalls caused by sideswipe and velocity are
turned into practical prediction tools.
seismic
lines across-domes and anticlines
normally exaggerate the size of the anomalies. Migrated
seismic
lines across synclines and basins are characterized
with false expressions which include grabens, contemporaneous
deformation, cross-stratification, high-amplitudes,
and crossing reflections. Geological areas that have large
lateral velocity contrasts, such as reefs, diapirs, or fault blocks
exhibit false
seismic
expressions. These include relief faults,
basement controlled tectonics, facies changes, and structures
which are located in geologically ambiguous positions. Even
the polarity of the
seismic
reflection is 3D dependent.
Modeling
examples show that interpretational pitfalls,
such as mapping from migrated sections and interpreting from
the basement upward, must be supplemented with pseudo-3D
interpretational techniques. Geologic models and their
seismic
analyses from salt provinces, reefs, overthrusts, etc., illustrate
these pseudo-3D interpretational tools.