Abstract: The postrift development of the Walvis Basin, Namibia; results from the exploration campaign in Quadrant 1911

HOLTAR, ERIK, and ARNE FORSBERG

In 1992 Quadrant 1911 was awarded as exploration licence 001 to a group consisting of Norsk Hydro (operator), Saga Petroleum and Statoil. Since then a total of 8000 km of seismic lines has been acquired, covering the 11,619 sq. Km large licence which is situated in the Walvis Basin. This basin was undrilled until the well 1911/15-1 was finished in early 1994. In mid 1995 well 1911/10-1 was drilled in the same quadrant, and a total of 4 wells are now drilled in the Walvis Basin.

The sedimentary succession of the Quadrant 1911 reflects a depositional history that post-dates the Neocomanian Etendeka plateau basalts found onshore Namibia. After the onset of the drift phase in late Hauterivian times, the Walvis Basin subsided and eventually a marine transgression took place. Shallow marine platform carbonates then prevailed until an Albian tectonic event resulted in complex block faulting and the formation of several sub basins. Subsequent volcanic activity created a series of volcanic centres localized near the Walvis Ridge bathymetric feature. In the Santonian the Southern African craton was uplifted relative to the shelf, leading to the formation of large-scale, westward-prograding wedges. Later sedimentation largely followed the evolution of a passive continental margin, responding to relative sealevel changes and paleoclimate.

A stratigraphic breakdown of the Northern Namibian offshore is proposed. It is suggested to divide the post break-up succession into seven major stratigraphic units or groups from W1 (= oldest) to W7, where W denotes Walvis Basin. Each group is described in terms of geometry, with examples on seismic expression and structural maps, and lithofacies as seen in well data.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria