3-D Poststack and Prestack Depth Migrated Seismic Data, An Advanced Interpretive Tool for Subsalt Exploration

William M. House, John A. Pritchett

The recent proliferation of regional, high quality 3-D seismic surveys in the Gulf of Mexico has provided a data base which is useful in understanding the relationships between salt techonics and hydrocarbon systems. Advanced seismic imaging techniques such as 3-D poststack and prestack depth migration have further improved the usefulness of these data. The 3-D poststack and prestack depth migrated data sets allow an interpreter to do much more than simply produce structure maps below salt. These data also provide a mechanism for detailed modeling of the subregional tectonoics, and an understanding of how those tectonics affect parameters such as trap timing, hydrocarbon migration and reservoir development. Correct spacial imaging of the data is provided by these depth mi ration techniques, allowing a true 3-D view of salt body geometries. The depth migrated data also show relationships between salt and subsalt reflectors at the salt/sediment interface. Evaluation of these data indicates that the emplacement, and subsequent collapse of allochthonous salt bodies by salt evacuation, is a process that has dominated the structural and stratigraphic development of the above salt section in many areas. The timing and nature of salt sheet emplacement and deformation has also affected the stratigraphic and structural development below salt. The prestack and poststack depth imaging of seismic data below salt allows for the creation of more accurate geological models of salt sheet emplacement. These models are critical in evaluating individual prospects. While the odels do not provide unique solutions, they do allow for the accommodation of all data in assessing risk with requards to trap timing, hydrocarbon migration, and the presence of reservoir quality sands.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995