Revisiting Models for Mini-Basin Development and Associated Fill Morphology and Architecture in Mobile Substrate Margins

Maharaj, Vishal T.¹; Wood, Lesli ²; Buttles, Jim ¹; Mohrig, David ¹
(1)Jackson School of Geosciences, University of Texas at Austin, Austin, TX. (2) Bureau of Economic Geology, Austin, TX.

Gulf of Mexico-centric models of mini-basin development have become the foundation for exploring and identifying strategic deepwater hydrocarbon reserves. Despite the abundance of subsurface data, little is known about the three-dimensional physical processes through which mini-basins fill relative to the topography created by underlying mobile salt. Our hypothesis is that mini-basins will show systematic changes in the geometry and morphology of the fill strata as accommodation conditions vary temporally and spatially relative to turbidity current properties. Therefore, for mini-basins undergoing deformation, systematic changes in these variables should be reflected in the geometry and morphology of the fill making up the strata.

The main objective of this research is to address pitfalls in the established models of mini-basin development using techniques in physical modeling to investigate mini-basin fill architecture, and to assess the ability to apply those learnings toward understanding subsurface datasets from minibasins developed in shallow-water and deepwater settings. Existing models are reviewed, and while they provide an ongoing framework, they are in need of revisiting in light of annual advances in our understanding of deep marine processes, deposit complexity and depositional system behavior in deep marine settings. In this research a three-phase approach is adopted, and includes: (1) physically modeling submarine flow behavior under conditions of varying topographic relief; (2) examining shallow-water mini-basin fills from the Gulf of Mexico that have evolved in settings undergoing active transition from low topographic relief to high topographic relief; and (3) examining deepwater fills in a rapidly-subsiding salt-withdrawal mini-basin from offshore Morocco.

In our analysis of mini-basin fill, stratigraphic geometries on various scales are used to develop a three-dimensional ponding index. The principle of mass conservation is applied to experimental turbidity currents to investigate the sediment trap potential of mini-basins given a particular morphology. These two parameters are linked to a turbidity current model, which can be used to predict stratigraphy in space through time. Relationships established from each phase of this research are subsequently integrated, and can be used to improve deepwater reservoir characterization as it applies to mini-basin provinces.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.