A Simulation Study of the Barents Sea Alta Discovery - Investigation of Optimal Recovery Method
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A re-occurring topic in the petroleum industry is to enhance the oil and gas recovery while optimizing the return of investment. Decisions related to field development are critical because most of the investments are made during the stage when the uncertainties are greatest. This thesis presents an optimization analysis of different development strategies for the Alta West discovery in the Barents Sea. Three development strategies are investigated: gas injection, water injection and pressure depletion. The Alta West is an oil discovery with a significant gas cap. The oil zone is 44-meter with an underlying aquifer. The reservoir is highly heterogeneous with clastic sandstones and conglomerates. The study is performed using the Eclipse Black Oil Simulator. The reservoir properties with inherent uncertainty are investigated. The most influential parameters for fluid production, relative to a deterministic reference case, are carried forward to an uncertainty risk analysis. The risk analysis is performed by using Monte Carlo Simulations. Each recovery method is evaluated and optimal recovery strategy is established, based on numerical simulations and other aspects of the field development process. The most influential parameters are permeability, degree of reservoir heterogeneity and the size of the underlying aquifer. Pressure depletion is regarded as the safest choice of development strategy taking into account the great uncertainties in the Alta West discovery. Gas cap expansion is considered a dominating drive mechanism. The results demonstrate that the gas cap displacement efficiency has a potential for high oil recovery without additional water- or gas injection. However, due to lack of infrastructure in the Barents Sea, gas re-injection or gas deposition might be required.