Aspects of the Deep-Water Potential, Offshore
NAMCOR (Pty) Ltd,
Recent drilling of exploration wells in
Namibia has proved that there are two
significant Cretaceous oil-prone source rocks offshore
Namibia, namely the Apto-Albian and the
Cenomanian. Previously the south-western coast of
Africa had long been regarded as being a
gas-prone region, based largely on the dry gas and source rock quality found in
the first well drilled in the Kudu gas field.
The Cretaceous paleogeography of the proto-South
Atlantic and its margins is important in
understanding the development, distribution and quality of these Cretaceous
source rocks. During the Aptian the proto-South
Atlantic was an anoxic basin with restricted
oceanic circulation. Northwards the Walvis-Rio Grande Ridge formed a
formidable barrier to movement of water. The ocean at this stage was only 500
km wide and oceanic circulation was restricted, with the Falkland Plateau still
being located to the south of the basin. In the distal, restricted parts of the
basin excellent, oil-prone source rocks developed that have hydrocarbon
generation potential in excess of 60kgHC/ton.
A younger oil-prone source rock of Cenomanian age has been
proven in the
Basin. The environment of deposition of this
source sequence is likely to have been anoxic where bottom water circulation
was poor or absent. This source rock is capable of generating large amounts of
oil but is immature in the well locations.
work on the condensates associated with the Kudu gas have shown that the
condensates were derived from a highly mature, marine, oil-prone source rock of
probable Cretaceous age.