Geological Reservoir Modelling and Process-Based Numerical Modelling of Deep-Water Distributive Systems from Detailed Outcrop Data: Examples from the Tanqua Depocentre, South Africa
David Hodgson1, Remco Groenenberg2, Amandine Prelat1, Wieske Paulissen2, Stefan Luthi2, Rochelle Steyn3, Jacobus Neethling3, and De Ville Wickens3
1Earth and Ocean Sciences, University of Liverpool, Liverpool, United Kingdom
2Geotechnology, Delft University of Technology, Delft, Netherlands
3Geology, Geography, and Environmental Studies, Stellenbosch University, Stellenbosch, South Africa
Lobes form in deep-water distributive systems that are the down-dip depositional record of sediment transported through channel systems on the slope, and can form important hydrocarbon reservoirs. The Permian Skoorsteenberg Formation in the Tanqua-Karoo Basin, South Africa, offers unique exposures to study the geometry, connectivity, and hierarchy of lobe elements, which are generally below seismic resolution. To better understand the sedimentary processes and deposit architecture of distributive systems, two modeling techniques have supported quantitative data collected from outcrop on lobe deposits.
Reservoir modeling software has been used to visualize composite lobes. Three models were constructed from different areas and stratigraphic intervals; Fan 2 at Kleine Gemsbok Fontein, Fan 3 at Gemsbok River, and Fan 4 at Zoutmeisfontein. Gradual and abrupt thinning trends in their lobe elements were recognised and found to be at variance with the simple sheet-like sandstone geometries typically envisaged. Field data collection resulted in estimates on the width, length and thickness range and stacking patterns of the sandbodies in the lobe elements.
The work also used a process-based numerical modeling package (FanBuilder) that includes parameters that govern turbidity current flow and deposit architecture, such as relief, flow density and grain-size distribution of the suspended sediment and their effects on lobe geometry. The model has been interrogated and calibrated with both 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 depositional topography.
AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery