--> Depositional Environment and Reservoir Heterogeneity of Bentiu Formation
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Previous HitDepositionalNext Hit Previous HitEnvironmentNext Hit and Reservoir Heterogeneity of Bentiu Formation (Albian-Cenomanian), Muglad Rift Basin

By

 Ayad M. Idriss1, Osman M. Abdullatif2, Omer A. Ali3

(1) National Research Centre, N/A, Sudan (2) KFUPM, Dhahran, Saudi Arabia (3) University of Khartoum, Khartoum, Sudan

 Bentiu Formation is a major oil Previous HitsandstoneNext Hit reservoir in the Muglad rift basin of interior Sudan. Subsurface lithofacies analysis allows the subdivision of Bentiu Formation in lower, middle and upper parts and each part is characterized by distinct facies assemblage and different Previous HitdepositionalNext Hit pattern. The lower part indicates deposition in moderately deep mixed-load high sinuosity stream showing transition to lacustrine delta. The middle part suggests deposition in low sinuosity braided sand-bed dominated stream. The upper part which is dominated by gravelly Previous HitsandstoneNext Hit and Previous HitsandstoneNext Hit facies indicates deposition in outwash plain of low sinuosity braided shallow channels.

The Previous HitsandstoneNext Hit facies range from trough and planner cross-bedded to massive and horizontally bedded Previous HitsandstoneNext Hit. Fine grained facies include rippled fine grained Previous HitsandstoneNext Hit and laminated to massive siltstone/mudstone facies. The facies assemblages suggest deposition within channels, bars, overbank and floodplain environments.

Large scale heterogeneity and dimensions of Bentiu Previous HitsandstoneNext Hit bodies and the siltstone/mudstone barrier/baffle units vary within the lower, middle and upper parts of the formation. Small scale reservoir heterogeneity includes Previous HitsandstoneNext Hit composition, grain size change and Previous HitdiagenesisNext Hit such as quartz overgrowth, clay infiltration and authigenesis, feldspar alteration and carbonate cementation and dissolution. The later appear to have Previous HitinfluenceNext Hit on secondary porosity production and enhancement

The reservoir heterogeneity of Bentiu Formation reflects the intra-basinal and extra-basinal control on the lacustrine/fluvial system through space and time. Understanding of these controls within a Previous HitdepositionalTop model framework is essential for the prediction and assessment of reservoir quality of Bentiu Formation.