Charles D. Winker2
(1) University of Leeds, Leeds, England
(2) Shell EP Technology Applications and Research, Houston, TX
Abstract: The Late Pleistocene Trinity-Brazos Turbidite System. New insights for deep turbidite reservoir interpretation
High frequency seismic data from shallow analogues provide an invaluable help to resolve what would constitute first-order sub-seismic elements in a conventional seismic survey. In this context we have studied the late Pleistocene Brazos-Trinity turbidite system which is exposed intact on the Gulf of Mexico continental slope. It lies immediately downdip of a lowstand shelf-edge delta and occupies four mini-basins linked ‘fill-and-spill’ style. The system forms onlap-fill successions which are entirely Wisconsinan in age (thus consists of a single 4th order sequence). It overlies thick hemipelagic deposits and can be subdivided into seismic stratigraphic units supported by well data. The following elements have been identified: turbidite complexes, debris flows, condensed sections, channels and levées. Analyses of seismic facies, well calibration, detailed mapping, and basin to basin correlation allowed us to:
- reconstruct a complex basin filling history made of repeated forward and backstepping of the system
- recognise the lithofacies distribution
- suggest an external (climatic) control on the deposition of 5th order sequences
- demonstrate that the last sequence within a glacial cycle is represented by a channel levée system and a mud-rich fan
- demonstrate that channel levée systems do not represent the first establishment of bypass to downdip basins.
The results of this study combined with the generation of synthetic seismic at lower frequency using a compacted model provide a powerful tool to better understand deeply buried turbidite systems.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana