Sedimentation Framework and Tectonostratigraphic Development of the Muglad Basin Sudan

Yasir M.A. Ghorashi, Sr.
GNOPC, Sudan
*[email protected]

The Muglad Basin, located in southwest Sudan, forma a major part of the Sudan Rift System, which in turn, is a main component of West and Central African Rift System . The rift started to develop during the Late Jurassic and Early Cretaceous times. This intra-continental rift system evolved through a three-phased tectonic history spanning Berriasian to Cenomanian, Coniacian to Maastrichtian and Paleocene to Pliocene. The sediments in the Muglad rift basin consist of Lower Cretaceous to Upper Tertiary non-marine cyclic sequences of lacustrine and fluvial/alluvial facies and directly rest upon the Proterozoic basement. Concentrating on the first rift cycle, this study reviews the sedimentation framework as a function of subsidence and thermal contraction. The database is mainly from proprietary exploration work consisting of 2-D and 3-D seismic data, well logs, core and borehole image logs. The Abu Gabra Formation is a typical argillaceous facies dominated by cycles of lacustrine shale prograding to deltaic sands. This lacustrine shale provides good hydrocarbon source rock while the deltaic sand proved to be a good quality reservoir. This cyclicity could be due to the fact that accommodation space was created by rift pulses rather than through continuous subsidence. After the cessation of rifting, thermal contraction probably occurred and created accommodation space, which was then gradually filled by the Bentiu Formation, consisting mainly of arenaceous fluvial sequences. These sands represent main reservoir units in the basin. Seismic data, logs and borehole image logs show a clear angular unconformity between Abu Gabra and Bentiu formations.

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain