The Relationship of Allocthonous Salt Withdrawal to Expanded Shelf Edge Sedimentation, Offshore Southeast Louisiana

Bruce A. Matsutsuyu, Kenneth O. McDowell, Kristian E. Meisling, and Raymond F. Barrett
BP, Houston, TX

Progradational sediment loading and associated lateral and vertical salt movement have created a structurally complex trend of growth faults and salt domes along the northern Gulf of Mexico shelf offshore southeast Louisiana. This is a region of prolific oil and gas production, yet deeper, more basin-ward sediments deposited during the time of most active salt evacuation remain relatively under-explored due to drilling depth, pressure concerns, and uncertainty of reservoir presence. Such basin-ward sediments, termed “Salt Evacuation Related Sedimentation” (SERS), are localized by accommodation space created by evacuating tabular salt bodies where shelf edge deposition loads the landward side of counter-regional salt ramps which act as feeders for the allocthonous salt. SERS may also be associated with low-displacement down-to-the-basin buried growth faults that develop in response to feeder evacuation, and can have unique distribution patterns due to the dynamics of salt movement and sedimentation. Most notable is the lateral continuity of sands which may extend down-dip to the abandoned salt feeder (weld). Insights into the location and distribution of these sediments is gained by understanding the timing and nature of salt evacuation and integrating that knowledge with regional sand trend mapping and “Voxel” (volume pixel) geobodies carefully extracted from appropriate 3D seismic volumes. The spatial distribution of geobodies not only readily illustrates the geometry and extent of the expanded shelf edge depocenter, but also demonstrates how sedimentation progressed as salt evacuation occurred. Application of this model and the described methodologies could reveal similar prospective areas for allocthonous salt-related shelf edge sedimentation.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas