Fan 2 deposits of the late Permian Tanqua-Karoo subbasin in South Africa are sheet sandstones typical of an outer submarine fan. The fan consists of three sand-rich units, separated by several meters of shale, that thin to the north and northeast into the Tanqua subbasin. The stacking pattern is progra-dational, with lateral offset to the east, suggesting that the lower units influenced the depositional location of those above.
Broadly lens-shaped beds, random vertical thickness trends, and variable paleocurrent directions suggest that sedimentation occurred through relatively broad, shallow pathways whose position changed frequently during deposition of the outer fan. The resulting sheet sand deposits have estimated dimensions of 3–10 km in a dip direction and 100–2000 m in a strike direction. These individual sheet sands, which laterally have relatively uniform sedimentary characteristics, stack to form depositional lobes.
Detailed outcrop-scale observations and measurements reveal that amalgamation and scouring are more prevalent than is initially apparent, enhancing sandstone connectivity both vertically and laterally. Shale clasts, bed-scale scours, and the three sand-rich units of Fan 2 represent three scales of geologic heterogeneity that would affect fluid flow in this type of reservoir.
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This Memoir covers one of the most important and active exploration reservoirs being pursued by geoscientists worldwide: fine-grained turbidite systems. 28 chapters show the results of an intense research effort in the 1990s that resulted from the discovery of large hydrocarbon accumulations in fine-grained turbidite systems in Brazil, the Gulf of Mexico, West Africa, and the North Sea. Industry and academia have joined together in this publication and the result is a unique opportunity to study these turbidite systems from the outcrop to the modeling; through the interpretation with 2-D and 3-D seismic data; to case histories and analog studies from Arkansas and Oklahoma, South and West Africa, Gulf of Mexico, west Texas, and New Zealand.