A brown field consisting of NE and SW accumulations has stacked six clastic and one carbonate reservoirs with fluid contacts per reservoir per accumulation. Depositional environment changes from shallow marine at the bottom to deltaic lacustrine at the top. Average rock properties and connectivity deteriorate from bottom to top.Borehole rugosity and low resistivity contrast between hydrocarbon and water bearing intervals made petrophysical evaluations difficult that may have led to STOIIP overestimations. Production allocations for commingled horizons were not carfully done.The tests in some wells have suffered from packer leak and/or flow behind the casing. These sealing issues have drastically increased uncertainty in aquifer support for upper reservoirs and in oil production for lower reservoirs.An integrated study with static and dynamic models was conducted to minimize uncertainties, risks and to optimize field development options. Well logs, and seismic, production, pressure, core, and PVT data in addition to well events are all incorporated into the models. Several IFT measurements were obtained at the start of the study and the results greatly reduced uncertainty in the height of capillary transition zones defined through 4 poro-perm and 5 capillary pressure models.Multiple static model realisations were constructed based on sequence stratigraphic correlations, facies geometries, porosity distributions and analogue depositional systems. These realizations were input to dynamic models to establish Base, High and Low cases with historically possible range of uncertainty and risks for the field development options.In conclusion, uncertainties were reduced from 120% to 10% after modeling and history matching identified active and passive STOIIP. Uncertainties in past production allocations were minimized via model well bore communications. Unconstrained development options lead to the optimum number of wells. After including drilling and surface facility costs, economics screening indicated that infill-drilling for the north-east and infill drilling supported with dump flooding for the south-west were the best options.The study is completed in 2008 and the resultant plan has been being implemented in phases. Phase I involved one NE producer in 2009 and one SW water injector in 2010. Producer W-12 was a success and has been producing with an initial rate that was three times the discounted expectation rate due probably to 5m shallower structure and twice thicker bulk thickness and better permeability.