This paper describes the application of compositional reservoir simulation techniques in the management of large reservoirs. The equation-of-state compositional simulator was specifically enhanced to address several technical challenges, such as geologic heterogeneities including crossing faults and widely varying permeability, complex phase behavior of a near-critical fluid, and involved surface facilities operational constraints.

The application of the simulator to the Oso field in Nigeria is presented. The Oso field has two reservoirs. This field study reports on the major reservoir which contains a near-critical fluid and has a highly faulted structure. The fault model, in addition to accurately representing geologic faults and the associated flow across different layers, also reduced computational requirements considerably over the old conventional methods for fault representation. The reservoir fluid and its behavior near the critical region was characterized accurately using an 8-component, equation-of-state model.

The application of the model in the study of reservoir recovery under various production scenarios is discussed. The displacement mechanisms involved in the different depletion strategies are explained through a series of 1-dimensional simulations. This integrated approach in reservoir management enables us to determine an optimal development plan and surface facilities design parameters for the Oso reservoir.

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