Reservoir production optimization using an upgraded perturbation gradient approximation algorithm

Key words:  reservoir  production optimization  approximate gradient  derivative-free algorithm  SPSA algorithm  EnOpt algorithm

Abstract:

Reservoir production optimization is a high-dimensional optimal control problem, and it is very difficult to obtain a true gradient. In this paper, a general perturbation gradient approximation method was presented, and the gradient resolved was always in uphill direction. The commonly used SPSA and EnOpt algorithms, being derivative-free, can be considered as special cases of the general perturbation gradient approximation. The perturbation gradient approximation can be upgraded by introducing an optimized lower triangular matrix for approaching to the true gradient. The numerical simulation results show that, compared with the standard SPSA algorithm, the optimization efficiency of the upgraded algorithm can be increased nearly 100%. In a real case study, the reservoir production optimization was conducted using the new method on the basis of history matching. The field data have shown remarkable increase on oil production and decrease of water production, and the sweeping efficiency of water flooding is significantly improved, which validates the feasibility of the algorithm for practical applications.