Kevin P. Corbett¹, Timothy B. Berge², Werner Leu³

(1) The Anschutz Overseas Corp, Denver, CO
(2) Forest Oil International Corp, Houston, TX
(3) Geoform AG, Winterthur, Switzerland

ABSTRACT: Low-hanging fruit in the Orange River Basin, South Africa

A major progradational delta system, comprising a first-order super sequence, developed in the southern Orange River Basin, South Africa from middle Albian through the end of the middle Turonian. This depositional system was characterized in the middle Cenomanian through middle Turonian by significant shelf-bypass, resulting in the development of three areally extensive composite deep water turbidite channel and fan systems. Time equivalent shelf deposition is dominated by a sand-rich distributary delta complex. Feeder channels from the shelf sands to the deep water fan system are localized by basement controlled rift transfer faults. Syn-depositional growth faulting served to localize deep water sand deposition and constrain fan depositional geometry, such that fans are oblate with long-axis parallel to fault strike. Continued development and landward migration of the growth fault system in response to deposition of the overlying upper Turonian through Maastrichtian sedimentary wedge enhanced structural closure. Preliminary geochemical maturation modeling of Cenomanian and Turonian age source rocks indicates most of the deep-water area is in the main to late-stage of oil maturation. The combination of well developed turbidite sand channel and fan reservoir systems, draping of the reservoir rocks across major roll-over anticlines, propitiously timed oil generation from interbedded source rocks, and a well defined high-stand flooding surface as a top seal, serve to make the deep water Orange Basin in South Africa the highest potential deep water area remaining along the west African continental margin.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado