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Reservoir Modeling of Samaa and Yabus Formation (Tertiary), Agordeed Field, Melut Rift Basin, Sudan

Badi, Amani A.*1; Ali, Omer A.1; Farwa, Abdalla G.1; Abdullatif, Osman M.2
(1) Geology, University of Khartoum, Khartoum, Sudan. (2) Earth Sciences, KFUPM, Dhahran, Saudi Arabia.

Melut rift basin has become one of the targets areas for hydrocarbon exploration in Sudan. This rift basin is regionally linked to the Central and West African rift system. The Agordeed oil field is one of the most productive oil reservoirs in Melut Rift basin of interior Sudan. The Tertiary Samaa and Yabus Formations, which are the main reservoir sandstones, occur at shallow burial depth were deposited within fluvial/lacustrine environment. This study aims to integrate 3D seismic data, well data and geologically interpret the inversion results within the framework of a consistent depositional model so as to understand the factors controlling the oil occurrence and distribution. In order to extract a volume of acoustic impedance from the seismic data Constrained Sparse Spike Inversion (CSSI) method has been chosen to generate an impedance model. Detailed 3D seismic imaging provided the subsurface morphology. 3D seismic interpretation results including facies analysis from seismic inversion combined with log and core data. The sand bodies geometries were predicted and delineated throughout the high resolution 3D seismic data and the impedance slicing. Horizon slices were used to examine the lateral variation of the seismic facies. The sand content increases toward the northern western part whereas the clay increases to southern eastern part of the basin in Samaa and Yabus intervals but the sand ratio of Yabus is less compared to Samaa on the same trend. The study area is highly affected by tectonics and faulting and this consequently affected the lateral continuity of the sand bodies within the basin in along the NW-SE trend and the SW-NE trend. The oil-bearing facies in Agordeed area are mainly delta-front sandstones in Samaa Formation that shows coarsening upward and blocky patterns and channel-fill sandstones that show both fining upward and block patterns in Yabus Formation. These sandstones are more continuous in the east-west direction than that in the north-south directions. The evolution of facies and environments through space and time as controlled by tectonics, faulting and other factors are influential in determining the meso to macro scale reservoir heterogeneity and quality.


AAPG Search and Discovery Article #90141©2012, GEO-2012, 10th Middle East Geosciences Conference and Exhibition, 4-7 March 2012, Manama, Bahrain