The Florida escarpment is one of the most dramatic bathymetric features in the Eastern Gulf. In places it reaches more than 1600m above the abyssal seafloor. Dips of 40 degrees are frequent, and vertical cliffs are not uncommon1. This feature along with geological complexities of carbonate and salt regimes present imaging challenges that are addressed through the use of:
• True azimuth 3D SRME
• Pre-stack Depth Imaging
• 3D imaging
• Anisotropic imaging
• Tomography
• Post-migration residual demultiple The long history of imaging in this area will be reviewed. Incremental improvements in data quality and interpretability will be shown. Processing efforts started with a grid of 2D lines using PSTM imaging algorithms. Subsequent efforts included SRME for multiple elimination, PSDM and tomography. Latest results are from modern 3D acquisition utilizing 3D true azimuth multiple elimination, anisotropic pre-stack depth imaging, and post migration residual demultiple.
TGS has a long history of collecting and processing data in this region of the Gulf of Mexico. The first major coverage of the area was two large 2D programs (see Figure 1). The lines were acquired in the late 1990’s. Total acquisition mileage was over 23,000 miles. The data was acquired on a 2km grid shot generally strike and dip to the escarpment feature. An infill survey on a 1km grid was shot in the DeSoto Canyon and Lloyd Ridge blocks. A portion of the initial processing of this survey included Kirchhoff pre-stack depth migration and 1D velocity updates. Subsequent reprocessing efforts in 2007 included SRME for demultiple, tomography for velocity updates, salt and carbonate layer velocity interpretation and Wave Equation pre-stack depth migration in addition to Kirchhoff pre-stack depth migration for the final imaging. The most current reprocessing of a portion of this survey added more detailed preprocessing as well as several more passes of tomography to high-grade the velocity model. In 2009 a 370 block 3D survey was acquired and processed over the Desoto Canyon area. Preprocessing included 3D true azimuth demultiple (TAME)2, Radon residual demultiple. Depth imaging tools included: VTI anisotropy, 3D tomography, salt body interpretation, VTI Kirchhoff pre-stack depth migration and VTI wave equation migration. Post migration interbed multiple modeling and subtraction were also done on portions of the final survey.
One of the main goals for the 2D reprocessing of the data in 2007 was to better image structures by refining the velocity model and to better attenuate the surface related multiples. SRME was used to better remove multiples. In general this proved to be quite effective, but as there is a significant 3D component to the waterbottom structure in the area of the escarpment it was not completely successful. An additional pass of Radon demultiple was used to attenuate remnant multiple energy. Deriving an accurate imaging velocity via tomography also provided some challenges. In the shallow water areas there was a somewhat thin layer of compacted sediments, followed by a fast velocity carbonate sequence.
