South Atlantic Margin South African Gas Systems

SAGS

Scope

Natural hydrocarbon seepage is a process recognised along most continental shelves. Gas chimneys are seismic indications of vertical gas migration and are often related to surface features including mud volcanoes, pock marks and carbonate mounds. Besides deep thermogenic hydrocarbon sources gas hydrate dissociation has been put forward as a possible hydrocarbon source. Major consequences of hydrocarbon seepage include the support of diverse biological communities, contribution to ocean and atmospheric composition and the potential to reduce the stability of continental margin sediments. The Orange Basin, South Africa, with its occurrence of mud volcanoes, pock marks and possibly gas hydrates, represents an ideal region for studies investigating the controls on the location, initiation and evolution of these surface and buried features as well as their potential significance for hydrocarbon exploration and influence on climate change. 

Methods

Seismic profile showing present day gas chimneys with seepage from the subsurface through the sea-floor

Seismic interpretation and borehole data are used to unravel the basin development and for mapping of gas seepage features. These data are then taken for further 2D and 3D petroleum system modelling. 

Areal distribution of mapped gas chimneys in the southern Orange Basin

3D-Petroleum system model predicting the gas migration pathways. The model will be used to understand the processes and to quantify gas seepage both currently and in the past

Contact

G. Kuhlmann
R. Di Primio
B. Horsfield


Partners

Performed as part of INKABA YE AFRICA
- Petroleum Agency South Africa
- University of Cape Town / Western Cape University
- Alfred Wegener Institute for Polar and Marine Research
- Bundesanstalt für Geowissenschaften und Rohstoffe

Funding bodies

GFZ Potsdam