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Abstract: This paper will focus on the vast deepwater areas of offshore South Africa; areas which require a challenging and expensive exploration effort. Latest exploration activities of Offshore South Africa, combined with a bit of exploration history will be discussed. This would then be compared with worldwide trends concerning deepwater exploration. Africa's important role within this new drive to exploit the world's deepwater hydrocarbon resources is also emphasized. General geology of the offshore basins will briefly be summarized, and the talk will coclude with the latest resource estimates of South Africa's deepwater areas.
INTRODUCTION During the past 30 years, exploration of the Mesozoic basins of offshore South Africa was generally restricted landwards of the 200m isobath, with only a few wells exploring the Orange Basin on the West Coast in water depths deeper than 400m. Off the South Coast these rigs could only manage in water depths of up to 300m maximum. The strong Agulhas current and adverse weather conditions imposed restrictions on the use of the existing semisubmersibles.
Exploration history The first offshore well in 1968 discovered the Superior gas field in the Pletmos Basin, which is a sub-basin of the Outeniqua Basin off the South Coast. Subsequently, most of the offshore exploration was then focussed in the Bredasdorp Basin, which led to production of the F-A, EM and satellite gas fields in 1992, which have been feeding the synfuel plant at Mossel Bay. First oil production from the Oribi oilfield followed in May 1997, a deep marine basin floor channel and fan complex (bff complex), and production was increased when the Sable oil, gas and condensate field came onstream in mid-2003.
The Orange Basin is defined by the extent of a sedimentary wedge that occupies about 150 000 km off the southwestern coast of Africa, and is more than 8 km thick in places. Although the basin is sparsely drilled with only 40 wells, most of which tested the shallow water areas, results thus far have been extremely encouraging. Two gas fields (Ibhubesi in South Africa, and Kudu in Namibia) with multi-TCF potential have been discovered within the younger geology, while the A-J1 well yielded an oil discovery in some of the oldest sedimentary fill.
The Ibhubesi gas field has recently been defined by Forest Exploration International, through appraisal drilling in the area of the original A-K1 discovery well. The tested wells in this field yielded a high combined flow rate of dry gas and condensate. Analysis of 2D and 3D seismic surveys in the area has defined many new prospects and justifies the extension of this play for some distance to the north.
The Durban Basin remains under-explored with only 4 wells testing the offshore areas close to shore, all of which were non-commercial.
World trends Studies of oil discoveries made during the nineties indicate that giant oil discoveries are more frequently found in the deepwater areas of the world compared with the shallower water regions.
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