AAPG/SPE Africa Energy and Technology Conference

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New Insights in the Evaluation of Reserves of Selected wells of the Pletmos Basin Offshore South Africa


The area evaluated has similar structural styles and settings as the producing neighboring fields of F-A and E-M in the adjacent Bredasdorp basin Offshore South Africa. The main objective of this study is to create a 3-D-static model and estimate hydrocarbon reserves. Based on log signatures, petrophysical properties and structural configurations, the reservoirs were divided vertically into three reservoir units in order to be properly modelled in 3-D space. The thicknesses of the layers were determined based on the vertical heterogeneity in the reservoir properties. Facies interpretation was performed based on log signatures, core description and previous geological studies. The volume of clay and porosity was used to classify facies into five units of sand, shaly sand, silt, and clay. From petrophysical interpretation, a synthetic permeability log was generated in the wells which ties closely with core data. The J-function water saturation model was adopted because it produced better results in the clean sandstone sections of the reservoirs. A high uncertainty in the basement formation was observed due to very few wells drilled in the area and fault impact and thus resulted in evaluation of uncertainty of each zone separately. The uncertainty workflow was run using 100 trials and the base case P50 estimated 277 Bcf of Gas from the 1At1.