One of the primary goals of the reservoir management is to enable decisions that maximize recovery from the reservoir. With recent developments in monitoring and control, the opportunity to optimize reservoir production through frequent adjustment of well controls has substantially increased. We recently proposed and demonstrated an improved ensemble-based production optimization method using Conjugate Gradient technique (CGEnOpt) on a synthetic reservoir model. The proposed method results in faster convergence as a result of using the conjugate gradient directions instead of steepest ascent search directions. The net present value (NPV) of a single reservoir is optimized by obtaining the gradient of the NPV from an ensemble of control variables.

In this paper, the benefits and effectiveness of the proposed method is demonstrated on a real field example located off-shore west Africa with 15 producers and 11 water injectors. The production and injection rates are used as control variables to maximize NPV of the reservoir.

The results indicate that the control settings from the proposed method result in a significantly higher NPV of the reservoir as compared to the reference case. The number of iterations needed for the proposed method is significantly reduced compared to the standard ensemble-based optimization. The proposed method is able to allocate the production and injection rates effectively which results in a substantial decrease in the amount of water produced.

In the literature, a wide variety of approaches were developed and implemented for optimizing the reservoir performance by adjusting operational controls. The proposed method is completely adjoint-free and is independent of the reservoir simulator used for the prediction simulation run which makes it easy to implement. It can be used with any existing simulator with minimal code development.

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