--> Abstract: Integrating a Suite of Geoscience Data Analyses with Basin Modeling to Understand the Development of the Orange Basin Hydrocarbon System, South Africa, in 4-D, by Douglas A. Paton, David Van der Spuy, Rolando Di Primio, and Brian Horsfield; #90039 (2005)

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Integrating a Suite of Geoscience Data Analyses with Basin Modeling to Understand the Development of the Orange Basin Hydrocarbon System, South Africa, in 4-D

Douglas A. Paton1, David Van der Spuy2, Rolando Di Primio3, and Brian Horsfield4
1 GeoForschungsZentrum Potsdam, Potsdam, Germany
2 Petroleum Agency SA, Cape Town, South Africa
3 GeoForschungsZentrum Potsdam, D-14473 Potsdam, Germany
4 Geoforschungszentrum, 14473 Potsdam, Germany

We document a 4D analysis of the Orange Basin hydrocarbon system, South Africa, through iteratively integrating available geoscience data with basin-modelling.

A high resolution geo-model of the Orange Basin passive margin evolution from Jurassic rifting through Early Cretaceous South Atlantic rift initiation to the establishment of the shelf margin is derived. The model is established by integrating a suite of geoscience data, including high resolution seismic, borehole, sedimentological, geochemical, structural, geophysical, and heat-flow analysis.

Following calibration to well data the 3D basin model was re-run taking hydrocarbon generation and migration into account. Known accumulations and gas seepage sites were used to fine tune the input and derive a final well constrained model of basin evolution in 4D. Proven source intervals are of Barremian and Aptian age, and from regional studies a Hauterivian syn-rift source has been inferred. Hydrocarbon generation started in the Aptian and was associated with the initial development of the passive margin. Sources are predominantly gas prone. Migration has principally been controlled by the occurrence of Aptian and Albian sand prone deltaic sequences, and structural/ stratigraphic closures associated with these sequences have resulted in localised accumulations. These accumulation sites have been long lived and have been charged a number of times.

Modelling results demonstrate that currently active gas seepage sites are structurally/ stratigraphically controlled, suggesting that paleo-seepage events have occurred. Modelled hydrocarbon losses through seepage were enhanced by an episode of differential uplift and erosion during the late Cretaceous, as well as by a subsequent Tertiary event.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005