Controls on the
Geometry and Internal Architecture of Submarine Fan Elements, Tanqua
Depocentre,
Groenenberg, Remco M.1, David
M. Hodgson2, Stefan M. Luthi3 (1) Delft University of
Technology, 2628RX, Delft, Netherlands (2) University of Liverpool, Liverpool,
United Kingdom (3) Delft University of Technology, 2628 RX Delft, Netherlands
The spatial distribution of grain sizes
in deepwater reservoirs is of primary importance in assessing production
potential. Grain size segregation in deep-water deposits is primarily caused by
changes in the hydrodynamic behavior of turbidity currents, which in turn is
controlled by flow density, initial sediment composition, and basin-floor
relief.
This study aims to investigate the
influence of turbidity current process (magnitude, density), sediment
composition (grain size range) and basin-floor relief on the architecture and
connectivity of basin floor fan elements in the Tanqua Depocentre, SW Karoo
Basin, South Africa. For this purpose, a process-based model has been developed
which simulates turbidity current flow, erosion, and deposition based on
principles of fluid dynamics that can deal with arbitrary basin-floor
topography and accommodates various grain sizes. It unifies conservation of
fluid mass, sediment mass and momentum in the form of the depth-averaged
shallow water approximation in combination with the Boussinesq approximation
for density-driven flow in three dimensions. Sediment transport is modeled by
an advection-diffusion type equation. Exchange of sediment with the bed is
largely based on existing models for entrainment and deposition. Input for the
model consists of parameters defining the initial basin-floor topography and
parameters related to the composition of the flows (size range, density,
magnitude and frequency of the flows).
The model is compared and calibrated with
high-resolution outcrop and borehole data. Results show how the internal
architecture and connectivity of the basin floor fans have been influenced by
initial flow composition (density, magnitude), sediment composition, and
basin-floor topography.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California