Fluvial sands with discontinuous interbeds and highly variable permeability patterns pose a significant challenge for further development of high water-cut oil fields with bottom aquifer in Sudan. To obtain an optimal strategy for further infill drilling a multi-disciplinary study of reservoir characterization and performance prediction was undertaken.

Data from vertical observation wells and deviated wells, combined with seismic horizon data and inversion data were used to characterize the spatial distribution of reservoir architecture and interbeds. Petrophysical properties (porosity and permeability) models were then stochastically simulated under such reservoir frameworks.

To avoid the distorted or zig-zag grids, vertical stair-step faulting upscaling method was taken to ensure that cells were orthogonal. Fine grids where interbeds most often occured were kept during upscaling to serve as vertical fluid flow baffle. The accurate coarse model that provided a realistic understanding of the lateral variation and distribution of reservoirs in inter-well areas were then taken as the base to effectively develop reservoirs.

During history matching, some scenarios were tested as alternatives in pursuit of a history match. The history matching procedure revealed the significance of interbeds as vertical prevention of water coning and permeability streaks as conduits to effectively drain reserves. Performance predictions for infill well cases are carried out based on the remaining oil distribution. The infill wells are optimized based on the incremental oil rate which can improve the cumulative oil production and recovery factor.

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