Artificial Gas Lift consists of gas injection into the tubing to reduce hydrostatic pressure loss. The oil produced from each well is a function of the gas injection rate. Some wells exhibit unstable behavior for low gas lift flow rates and the excessive use of gas causes a reduction in the production of oil due to high friction losses. Therefore the gas lift flow rate must be kept in a bounded interval. For a given amount of gas used, the production of oil varies significantly between wells, so the objective of gas lift optimization is to allocate a limited amount of gas to a number of wells in order to obtain the maximum oil production (or profit). Evolutionary algorithms were applied to achieve optimal production rates and decide which well must be closed when the compression capacity is severely reduced. The FPSO considered in this study is equipped with three _choke2Fcompressors to produce 16 wells with gas lift and export gas. Eventually, one or two compressors can have a downtime due to maintenance requirements or failures. In this case, at least one well has to be closed. The algorithm was developed to optimize the production when the compression capacity was reduced and decide which well should be shut-in. It takes into account not only the total amount of gas available but also the gas lift pressure, which can change over time. The algorithm solved a practical gas lift optimization problem and was able to automatically determine which wells had to be closed in order to produce the maximum amount of oil whenever the total gas available was not enough to simultaneously operate all wells. For the cases where the total gas available was high enough that all wells could produce, the results obtained by this genetic algorithm were equivalent to any ordinary optimization algorithm. The production optimization is an important issue even during abnormal operation conditions. The water cut increases with the aging of wells and the gas lift flow rate demand also increases. Severe compression limitations are undesirable but they can eventually occur.
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