Abstract

Gas-lift is an important artificial lift strategy for increasing the production of hydrocarbons from heavy oil and offshore reservoirs with declining pressure. The optimum design and operation of gas-lift has a considerable impact on the optimum production and economics of the entire field and can only be achieved by considering all related variables in connected reservoirs, gas-lifted wells and facilities. Therefore, it is essential to formulate the gas-lift model as an optimization problem within an integrated modeling environment, where all the time dependent physical and operational constraints of reservoirs, wells and facilities can be collectively taken into account during the time evolutionary modeling of the asset. However, this could pose a computationally challenging problem for most derivative based optimizers, as some of the governing equations and models representing the gas-lifted asset could be very nonlinear, physically or mathematically discontinuo us, and the system may not have a solution under some of the conditions proposed by the optimizer due to physical operational restrictions or infeasibility. To overcome these problems we applied a mesh adaptive direct search (MADS) derivative free optimization technique to optimize the gas-lift problems in an integrated reservoir, wells and production facilities environment. The results proved the suitability of the MADS strategy for optimizing these systems particularly for systems with narrow or discontinuous boundaries of physical operation.

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