Testing the feasibility of proxy-based metamodeling for the CO2-GAGD process optimization

Document Type

Conference Proceeding

Publication Date

1-1-2016

Abstract

Unlike these Continuous Gas Injection (CGI) and Water-Alternating-Gas (WAG) injection modes, the Gas-Assisted Gravity Drainage (GAGD) process takes advantage of the natural segregation of reservoir fluids to provide gravity-stable oil displacement. Specifically, the gas is injected through vertical wells to formulate a gas cap to allow oil and water drain down to the horizontal producer (s). Therefore, the GAGD process was implemented through immiscible injection modes to improve oil recovery in a sector of the main pay/upper sandstone member in the South Rumaila oil field, located in Iraq. The Design of Experiments (DoE) and Response Surface Methodology (RSM) were employed to create as a simplified alternative proxy model to the compositional reservoir simulator for the CO2-GAGD process performance optimization. The CO2-GAGD process feasibility was investigated for the immiscible injection mode through the EOS-compositional reservoir simulation to obtain the optimal future performance scenario. After conducting the acceptable history matching, the Latin Hypercube Sampling (LHS) was employed as a low-discrepancy and more uniform approach to creating hundreds of simulation runs (experiments) in order to construct a proxy-based optimization approach. More specifically, the proxy model represents a metamodel used to evaluate the various designed experiments in the optimization procedure rather than the simulator itself. Then, the second-order polynomial equation was iteratively constructed and validated based on the response surface methodology. The optimization process searches about the optimal solution that represents the optimal set of levels of the operational decision factors. These decision factors include maximum oil production, minimum BHP, maximum water cut, skin factor in the production wells in addition to the maximum gas injection rate and maximum injection pressure in the injection wells. The cumulative oil production was handled as the response parameter that is calculated initially by the compositional reservoir simulation for 10 years of future production. The cumulative oil production by the end of the prediction period through this optimization approach has led to obtaining 4.6039 MMMSTB of oil production. However, the base case of the GAGD process evaluation of default parameters' setting has resulted to 4.3887 MMMSTB of oil production. Therefore, the current optimization approach has led to increasing the oil recovery by 215.2 million STB in 10 years of future prediction.

Publication Source (Journal or Book title)

International Petroleum Technology Conference 2016, IPTC 2016

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