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SWLGS Luncheon Topics

Updated January 20, 2004

Prestack Depth Imaging in the Eastern Gulf of Mexico: An Underexplored Petroleum Province
Robert V. Schneider; Director, Energy Institute - University of Louisiana at Lafayette


Abstract Summary: 

In anticipation of OGS lease sale 181, a large 2-D seismic dataset was collected in the eastern Gulf of Mexico (Lloyd Ridge and DeSoto Canyon). Primarily in deep water, approximately 3270 miles of seismic data were acquired and processed for regional understanding of eastern GOM geology. It was subsequently determined that pre-stack depth migration (PSDM) might be useful in identifying sub-salt features. Before committing PSDM to a large portion of the survey, a test was performed on a single line taken parallel to ocean bottom dip. Velocity model building was performed from a 'seed' model. Updates were derived by iterating PSDM and velocity analysis.

Results show that PSDM improves the imaged section in several important areas within the test line. In an environment in which deep water post-Jurassic movement is related to salt tectonics, salt lies primarily below and within a carbonate sequence underlying the clastic section. Penetration of salt into the Tertiary clastics is rare in comparison to GOM environments to the north and west. Interval velocities derived from the study demonstrate that salt may be faster or slower than the carbonates, generally depending on depth. Proper handling of this phenomenon yields improvement in basement imaging. Subtle structures spatially related to underlying salt diapirism can be observed near the base of the deep water clastic sediment section.

PSDM imaging also aids the understanding of the nature of the transition between shelf and deep water environments. The presence of the Florida Escarpment, a steeply-dipping shelf break, imposes anomalous underlying velocities which extend into the sub-shelf column. In fact, PSDM was unable to solve these velocity anomalies on its own. This fact led to the imposition of user-defined velocities under the shelf section in order to honor regional geologic realities. Where sediments and velocities remain relatively simple in deep water Tertiary sediments, PSDM does not produce a significant improvement over time imaging (pre-stack time migration).

Biographical Sketch: 

Born: St. Paul MN

Education:

B.S. Geology 1981, University of Minnesota, Duluth
M.S. Geophysics 1985, University of Texas at El Paso
D.Sc Geological Sciences 1990, University of Texas at El Paso

Employment:

1988-1997: Geophysicist, Amoco Production Company
1997-1998: Senior Research Geophysicist, Texseis/BHP
1998-2000: Senior Geophysicist/Project Manager, GX Technology
2000-2002: Chief Geophysicist, Spectrum Energy and Information Technology
2002-Present: Associate Professor of Geology and Director, Energy Institute,
University of Louisiana at Lafayette