Stock Tank Oil Initially in Place (STOIIP) uncertainty have been raised recently as a major impact on development plans of mature oil fields under the current tough economic conditions. One of the most complex reservoirs in Gulf of Suez is the Nezzazat group that has a high degree of lateral and vertical heterogeneity. Reservoir productivity and injectivity of such heterogonous reservoir require a high quality 3D geo-cellular model and a robust dynamic history match. However, the intersected lobes of bars and channels of in such heterogeneous concealing underneath a thick salt succession are very difficult to interpret and therefore impose a profound integrated study. This involves petrophysical characterization of Nezzazat group into seven hydraulic flow units honoring the lithostratigraphy of the basin, Mattula, Wata and Raha formations. To enhance field development plan, the Big Loop simulation approach is applied to cover all the existing geological uncertainty. This model honors the available dynamic data including static reservoir pressure, repeat formation tester data, injection and production logs in both history matching and prediction phases.

The 3D dynamic simulation model achieved history match to the seven reservoir intervals using RFT pressure data and production logs on layer basis, showing a wide range of permeability and contribution. The history matched model has successfully proved that the dynamic STOIIP is higher than the previous volumetric STOIIP with additional ±7 MMBO. This opened a window towards drilling new well to increase the current recovery factor for the field and achieve the new ultimate recovery. Therefore, the proposed methodology not only checks the validity of volumetric STOIIP calculations but also helps understanding hydraulic flow units architecture under uncertainty to increase the ultimate recovery of the mature fields.

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