--> --> Integrating 3-D Basin Modeling Concept to Determine Source Rock Maturation in the F-O Gas Field, Bredasdorp Basin (Offshore South Africa)

2018 AAPG International Conference and Exhibition

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Integrating 3-D Basin Modeling Concept to Determine Source Rock Maturation in the F-O Gas Field, Bredasdorp Basin (Offshore South Africa)

Abstract

The burial, thermal and petroleum generation history of the F-O Gas Field, Bredasdorp Basin have been studied using 3D basin modelling technique. The studied basin evolved around mid-late Jurassic to early Cretaceous times when Southern Africa rifted from South America. 2D seismic profiles and well data were upscaled into a 3D structural model of the basin. Four source rock intervals namely; Hauterivian, Barremian, Aptian and Turonian were incorporated into this study. At present-day, Turonian source rock is mainly in early oil (0.55-0.7% VRo) window. While the Aptian and Barremian source rocks are in the main oil (0.7-1.0% VRo) window, the Hauterivian source rock is mainly in the main oil (0.7-1.0% VRo) to late oil (1.0-1.3% VRo) window. Petroleum generation begins in late Lower Cretaceous, corresponding to high heat flow and rapid subsidence/ sedimentation rates. For all the four source rocks, the northern domain of the modelled area show low transformation ratio, indicated by low maturity values that are attributable to less overburden thickness. The Barremian and Aptian source rocks are the main petroleum generators, and both show very high expulsion efficiencies. However, the younger Aptian source rock could be regarded as the best source rock in the due to its quantity (i.e. highest TOC of 3%), quality (Type II with HI values of 400) and highest remaining potential. At present-day, ~1209 Mtons of hydrocarbons were cumulatively generated and peak generation occurred at ~43 Ma with over 581 Mtons generated. Finally, the results of this study can directly be applied for play to prospect risk analysis of the F-O gas field.