Simulation optimization of water-alternating-gas process under operational constraints: A case study in the Persian Gulf

Optimizing the efficiency of WAG flooding projects can guarantee the success of these projects. Many operational constraints can indirectly affect the flooding efficiency. Their effects is not normally considered during routine optimizations. The main aim of this study is to find the influence of these constraints (e.g., maximum water-cut, maximum GOR, and minimum BHP during WAG process). Implementing a reservoir simulator coupled with a simulating-annealing (SA) enables us to discover the effects of these constraints during simulation optimizations. The developed optimizer is applied into a case study from an Iranian formation located in the Persian Gulf. The recovery factor of WAG flooding is compared with that of the conventional waterflooding and gas injection. Moreover, the optimization of individual and simultaneous WAG parameters are analyzed. Results indicate that a) operational constraints not also can alter the production mechanism but also they directly affect the ultimate recovery factor; b) the recovery factor of simultaneous optimization of all WAG parameters is higher than that of individual parameter optimization; c) irrespective to the manner of parameter optimization, WAG ratio (or the volume fraction of injected water to gas) remains almost constant during all optimizations, showing the influence of this parameter during WAG flooding scenarios.