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Abstract
The thick sandstone sequences of the Bentiu-1 Reservoir Interval represents the most prolific oil bearing zones in the northeastern part of the Muglad Rift Basin. However, the lithofacies heterogeneity coupled with rifting complex structural and stratigraphic settings have resulted in complex reservoir geometries and highly variable petrophysical properties. This study aimed to establish a 3-D stochastic geocellular model characterizing the lithofacies heterogeneity and major reservoir architectures that control the reservoir properties and consequent fluid flow pathways. A comprehensive lithofacies classification, petrophysical analyses, and stochastic modeling workflow were used to deliver the objective of this study. The lithofacies classification revealed the prevalence of thee distinctive lithofacies: sand, shaly-sand, and shale. The petrophysical analysis of the porosity, permeability and water saturation revealed that these properties occur over specific zones. These zones, in turn, were easily correlated with the lithofacies identified. Four locally fining upward lithological cycles have been observed from the 3-D stochastic simulation of the lithofacies. Each one of cycles dominated by sand at the bottom and capped with shale at the top. The 3-D stochastic models of the petrophysical properties have confirmed the results of the lithofacies modeling. Four petrophysical units were firmly identified by the presence of three marker-beds. The marker beds were characterized by low porosity, low permeability and high water saturation corresponding to the shale situated at the top of each unit. The findings of this study provided a detailed structural, geological and petrophysical models for the Bentiu-1 reservoir Interval. These findings increase the current knowledge understanding and prediction of the reservoir geometries and reservoir potential in addition to providing a new insight into the petroleum exploration and future development of the study interval.
