Unlike continuous gas injection and water-alternating-gas injection, gas-assisted gravity drainage (GAGD) takes advantage of the natural segregation of reservoir fluids to provide gravity-stable oil displacement. The feasibility of carbon dioxide (CO2) GAGD was investigated for immiscible injection through equation-of-state compositional reservoir simulation with design of experiments (DOE) and proxy modeling to obtain the optimal future-performance scenario. After history matching, Latin-hypercube sampling (LHS) was used as a low-discrepancy and more-uniform DOE approach to create hundreds of simulation runs to construct a proxy-based optimization approach.
Many enhanced-oil-recovery studies have been conducted for CO2-flooding optimization in real oil fields; however, to the best of the authors’ knowledge, no study has been made for GAGD implementation and optimization in a real oil field. To implement the optimization process, a full compositional reservoir simulation was constructed to evaluate the reservoir performance through CO2-GAGD flooding for 10 years of future reservoir prediction. Then, proxy-model optimization was conducted through manipulating the operational decision factors that influence the CO2 flooding through GAGD by means of DOE. More specifically, DOE and proxy modeling were combined to create a simplified alternative (metamodel) to the compositional reservoir simulation to optimize the operational decision factors affecting GAGD. Four proxy models were adopted and validated as metamodels for the compositional reservoir simulator: polynomial proxy model, multivariate additive regression splines (MARS), fuzzy logic/genetic algorithm, and generalized boosted modeling (GBM)....
Proxy-Based Metamodeling Optimization of Gas-Assisted-Gravity-Drainage Process
01 October 2017