The syn-rift Organic Bucomazi is the source rock associated with the majority of oil accumulations in central West Africa. A new pre-salt source rock, the Falcao Deepwater, is younger and exists in thermal subsidence sag basins west of the Atlantic hinge. This source rock is different, geometrically and geochemically, from the older Organic Bucomazi. Unlike the syn-rift Organic Bucomazi, the Falcao Deepwater is not offset by the rift faulting and is sub-parallel to the base of salt rather than to the rotated basement blocks.

The pre-salt Falcao Deepwater source rock was discovered in the Falcao-1 well drilled in the offshore Kwanza Basin, Angola. It is laterally extensive with over 200 meters of 3 to 6% TOC (values may go as high as 9.5%). At a depth range of 3,700 to 4,150 meters, the source was at peak maturity (Ro1.3) and flowed 26.7°API oil to the surface from fractures in the source interval. The Falcao Deepwater source rock has the ability to charge deep water prospects where the organic Bucomazi is overmature and the post-salt section is immature.

Sag basin geometry and facies distribution (clastic shorelines, carbonate mounds, and source rock basins) are illustrated on speculative seismic data and will be shown on data provided by Geco-Prakla. Modern rifts (the East African Gregory Rift in Kenya and the southern Rio Grande Rift in New Mexico) display many of the characteristics underlying these ancient sag basins. Field studies in these modem rifts will be shown to illustrate the scale and depositional environments preceding the deposition of the Falcao Deepwater source rock.

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