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SWLGS Luncheon Topics

Updated August 05, 2003

January 2000

Sub-Salt Imaging in Walker Ridge, Gulf of Mexico
Jerry Young, Carl Hotfors, Xiaoquang Meng, Peter Montecchi, Veritas DGC

Abstract: Walker Ridge is located in the deepwater Gulf of Mexico, approximately 250 miles southeast of New Orleans. Shallow allochthonous salt sheets cover most of the area northwest of the Sigsbee Escarpment. Regional studies indicate that compressional structures of the Mississippi Fan Foldbelt extend southwest into the sub-salt section of Walker Ridge area. However, the high-velocity salt bodies distort the sub-salt data and impede the imaging and identification of sub-salt compressional structures. Nonetheless, recent discoveries including Mad Dog and Crazy Horse along the Foldbelt trend have significantly increased leasing and exploration activities in the Walker Ridge area.

As a result of surging interest, a regional 3-D pre-stack depth migration project covering more than 250 OCS blocks was initiated in early 1999. The objectives are to improve the interpretability of the sub-salt section and to enable the identification of compressional folds beneath the salt for prospect delineation. In the first part of the presentation, we will show examples of a series of 3-D pre-stack depth migrated target lines to illustrate the benefits of depth imaging and the complexity of sub-salt structures. Next, we will review the model building and QC procedures that were used to integrate interpretation and processing. Finally, we will discuss how we evaluate imaging parameters using results from a travel time sensitivity study.

The resulting depth images show improved sub-salt stratigraphic and structural detail, particularly sub-salt folds and faults. These features appear to be genetically influenced by deeper compressional structures. Sub-salt fault patterns further reveal a tectonic trend along a northwest direction.

Biographical Sketch: Jerry Young is Manager of Depth Imaging for Veritas GeoServices in Houston. He previously worked with the Exxon Production Research Company and the Exxon Company USA in various leadership roles in high-end seismic imaging research and applications. In addition to depth imaging, he has worked with data from major basins around the world in steep-dip imaging and amplitude preserving processing. He holds an MS in Geophysics from the University of Southern California and a BA in Geology from the National Taiwan University.