Abstract:

This report describes numerical techniques developed to determine the gas-lift configuration that will optimize the lifetime value of a property. The production history of a reservoir can be predicted by integrating a reservoir model, a wellbore flow model, a choke model, and a separator model. Changes in any production parameter, including the gas-lift configuration, will cause changes in the predicted production history. The numerical methods can find the combination of production parameters that maximizes the net present value of the flowstream. The control parameters explored include tubing diameter, separator pressures, depth of gas injection, and volume of gas injected. Each of these parameters may vary with time. The influence these parameters have upon the net present value is complicated by the feedback nature of the gas-injection loop. This nonlinearity requires robust, efficient routines for optimization. The optimizing model is used to demonstrate that both objective function (net present value), and optimal production parameter values can be very sensitive to uncertainty in the known reservoir data. This sensitivity study also illustrates a method of determining the value of additional reservoir data.

This report describes how to fashion an integrated wellbore and reservoir model, including the difficult feedback aspects of gas-lift. Additionally, insight is granted into the sensitivity of optimized parameters to uncertainty in reservoir data. Polytope and genetic algorithm optimization techniques are shown to be both stable and efficient when used to optimize these sorts of nonlinear optimization problems.

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Copyright 1996, Miles Robert Palke: Please note that the reports and theses are copyright to their original authors. Authors have given written permission for their work to be made available here. Readers who download reports from this site should honor the copyright of the original authors and may not copy or distribute the work further without the permission of the author, Miles Robert Palke.