Thesis (M.Eng.)--Chulalongkorn University, 2006

This report describes techniques developed to optimize net present value by designing completion, schedule of production and amount of gas injection for gas lift purposes. In the design of a production system, the determination of production parameters such as tubing diameter, choke diameter, pipeline diameter, separator pressures, volume of gas injected and number of wells are crucial in obtaining the optimal economic value of a project. The production profile of a reservoir can be predicted by integrating reservoir model, wellbore flow model, choke model, flowline model and separator model. Production profile changes with different sets of completion and production parameters including gas-lift configuration. The parameters that affect production rate are tubing diameter, choke diameter, pipeline diameter, separator pressures, volume of gas injected and number of wells. Some of these parameters may vary with time. After the production profile is obtained, NPV is calculated in the economic model. To find the maximum net present value, instead of calculating all sets of production parameters, nonlinear optimization technique is used in order to reduce computation time. Genetic algorithm has been chosen for this project. Three case studies with different reservoir and economic conditions were performed to see the effectiveness of genetic algorithm in finding the solution and the effect of each parameter on NPV.