Effects of salt-related mode conversions on subsalt prospecting
- Texaco Exploration and Production, Inc., New Orleans, LA (United States)
- Texaco E and P Technology Division, Houston, TX (United States)
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 hindrance 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 suggest some simple techniques that can assist an interpreter in the 3-D interpretation of subsalt events.
- OSTI ID:
- 218393
- Journal Information:
- Geophysics, Vol. 61, Issue 2; Other Information: PBD: Mar-Apr 1996
- Country of Publication:
- United States
- Language:
- English
Similar Records
A subsalt prospect in offshore Louisiana - evolution of a prospect from lease to present
Mahogany: Seismic technology leading to the first economic subsalt field