Print this pageUse of Fundamental Geological Knowledge in a Revisit of the Algoa and Gamtoos Basins, Offshore South Africa
The Algoa and Gamtoos onshore and offshore Mesozoic basins are located along the south eastern margin of South Africa. Late Triassic extension heralded the Mesozoic break up of Gondwanaland, beginning with Middle Jurassic rifting, resulting in the development of these and several other (half) grabens over an area presently located along the South African southern margin and its conjugate Falkland Plateau. With east and west Gondwana break up during Early Cretaceous, opening of the Atlantic Ocean developed along the Agulhas-Falkland Fracture Zone, separating the Falkland Plateau and Malvinas Basin from the African plate.
The Algoa and Gamtoos half grabens are separated by Paleozoic basement arches. The early rift fill of these half grabens consists of thick sediments containing Kimmeridgian - Portlandian wet gas to oil prone shales. The late rift fill comprises shelf, shallow marine, lacustrine and fluvial deposits, with sandstones of reservoir potential. The rifts are overlain by Aptian to Lower Albian fill of the Gamtoos and Algoa canyons. The larger of these, the Algoa Canyon, is a dramatic regional feature 10 to 30 km wide, up to 2 km deep extending 60 km in a south easterly direction across the Algoa Basin, containing channel sandstone with reservoir potential. Basement, the half grabens and canyon fill are in turn overlain by Albian sediments.
New African Global Energy holds a one year Technical Co-operation Permit during which all data is being reviewed. Nine of the twenty offshore wells encountered oil and / or gas shows with many unanswered questions remaining. New studies include sedimentological and reservoir assessments; thermal history reconstruction, and the integration of thermal history constraints, principally derived from apatite fission tract AFTA and VR data from wells and outcrop samples. The data derived from the thermal history reconstruction, aided by the tectono-stratigraphic framework to construct and run constrained basin models, aiding answering key questions upgrading the petroleum potential and prospectivity of this 12 000 square km poorly explored portion of the South African offshore.
AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil