Assessing 3D Structural Uncertainties in Reservoir Modeling and their Effects in Fluid Distributions and Dynamics

Using a study of a shallow offshore field in the Niger Delta we demonstrate the strength of combining different models to obtain multiple realizations of a geological and reservoir simulation model. The study represents an elongated roll-over anticline with multi-stacked reservoir sequences of hydrocarbon bearing sands. Apart from major fault blocks, the field shows a dense pattern of a conjugate system of synthetic and antithetic faults with the potential for complex sealing patterns. In this study we use two realizations of the fault model. One holding a simplified population (only major faults) and one with a larger population (major faults + minor faults). For this study the models are combined with identical stratigraphic models and identical property modeling parameters to evaluate the impact of the small faults on the fluid flow. Subsequent reservoir simulation results confirm a significant impact with production differences in the order of 20% between the two model realizations. The modular approach of combining model building blocks like fault models, stratigraphic models and the resulting structural models may also form the basis for uncertainty assessment related to structural constraints.