Core, Log, and Seismic Character of a Complete Shallow Marine to Deep Marine, Basin Floor 3rd Order Depositional Sequence: The 14A Albian Low-Stand Wedge of the Bredasdorp Basin, Republic of South Africa
Jeffrey B. Aldrich, Tamlyn Gourrah, Sakia Madiseng, and Jim R. Turner
PetroSA, Cape Town, South Africa
The Middle Albian 14A siliclastic sequence in the Bredasdorp Basin of South Africa has been penetrated by over 150 wells and has been recognized as a commercial target since oil was discovered in the E-AA1 borehole in 1986. During 1988, a detailed sequence stratigraphic study of the Bredasdorp Basin was carried out under the auspices of the University of Texas at Austin. This has, since then, resulted directly in a number of geological models being proposed. The 14A 3rd Order depositional sequence has been variously characterized as a) base of slope slumps; b) Low angle lowstand progradational incised channels; c) massflow deep marine sheet sandstones; and d) retrogradational confined flow deposits.
Using extensive core, log and 2D and 3D seismic data we document the variable nature of the 14At1 sequence boundary and the nature of the deposition on the unconformity from the eastern shelf, across the slope and into the abyssal plain of the Bredasdorp Basin. Across the transect we document extensive erosive channels and bypass zones, base of slope deposits, intermediate and distal fan deposits and the changing nature of both the well log and seismic character of the sequence boundary.
AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery