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GEOREF RECORD

Effects of salt-related mode conversions on subsalt prospecting

Jeff S. Ogilvie and Guy W. Purnell
Effects of salt-related mode conversions on subsalt prospecting
Geophysics (April 1996) 61 (2): 331-348

Abstract

Mode conversion of waves during seismic reflection surveys has generally been considered a small phenomenon that could be neglected in data processing and interpretation. However, in subsalt prospecting, the contrast in material properties at the salt/sediment interface is often great enough that significant P-to-S and/or S-to-P conversion occurs. The resulting converted waves can be both a help and a hinderance for subsalt prospecting. A case history from the Mississippi Canyon area of the Gulf of Mexico demonstrates strong converted-wave reflections from the base-of-salt that complicate the evaluation of a subsalt prospect using 3-D seismic data. Before and after stack, the converted-wave reflections are evident in 2-D and 3-D surveys across the prospect. Ray-tracing synthetic common midpoint (CMP) gathers provides some useful insights about the occurrence of these waves, but elastic-wave-equation modeling is even more useful. While the latter is more time-consuming, even in 2-D, it also provides a more realistic simulated seismic survey across the prospect, which helps to reveal how some converted waves survive the processes of CMP stack and migration, and thereby present possible pitfalls to an unwary interpreter. The insights gained from the synthetic-data study suggest some simple techniques that can assist an interpreter in the 3-D interpretation of subsalt events.


ISSN: 0016-8033
EISSN: 1942-2156
Coden: GPYSA7
Serial Title: Geophysics
Serial Volume: 61
Serial Issue: 2
Title: Effects of salt-related mode conversions on subsalt prospecting
Affiliation: Texaco Exploration and Production, New Orleans, LA, United States
Pages: 331-348
Published: 199604
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 10
Accession Number: 1996-032560
Categories: Economic geology, geology of energy sourcesApplied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch map, 2 tables, sects.
N28°00'00" - N29°00'00", W90°15'00" - W89°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
Update Code: 199611
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