Proxy Model Development for the Optimization of Water Alternating CO2 Gas for Enhanced Oil Recovery

• Published in: Energies (Basel) 2023-04, Vol.16 (8), p.3337
• Main Authors: Matthew, D Aqnan Marusaha, Jahanbani Ghahfarokhi, Ashkan, Ng, Cuthbert Shang Wui, Nait Amar, Menad
• Format: Article
• Language: English
• Subjects: Behavior; Carbon; Carbon dioxide; CO2-WAG; CO2 storage; Design optimization; Emissions; Energy economics; Enhanced oil recovery; Environmental tax; Fractured reservoirs; Gas injection; Genetic algorithms; Injection; Multiple objective analysis; Neural networks; NSGA-II; Oil; Oil recovery; Optimization; optimization study; Pandemics; Project feasibility; proxy model; Renewable resources; Reservoir design; Reservoir engineering; Sorting algorithms; Water injection
• ISSN: 1996-1073; 1996-1073
• DOI: 10.3390/en16083337

Optimization studies are an important task in reservoir engineering practices such as production optimization and EOR (Enhanced Oil Recovery) assessments. However, they are extensive studies with many simulations that require huge computational effort and resources. In terms of EOR, CO2 injection is one of the most common methods employed due to a high recovery potential and environmental benefits. To assess the feasibility of CO2-EOR projects, a reservoir design study must be conducted before optimization is performed. Some studies have demonstrated the advantages of employing proxy models to perform this task in terms of saving huge amounts of computer memory space and time. In this study, proxy models were developed to solve a multi-objective optimization problem using NSGA-II (Non-dominated Sorting Genetic Algorithm II) in two selected reservoir models. The study was performed for a CO2-WAG (Water Alternating Gas) application, where gas and water injection rates and half-cycle lengths were assessed to maximize the oil recovery and CO2 stored in the reservoir. One model represents a simple geological model (the Egg Model), while the other represents a complex model (the Gullfaks Model). In this study, the good performance of the proxy models generated accurate results that could be improved by increasing the amount of sampling and segmenting the behavior of the reservoir model (depending on the complexity of the reservoir model). The developed proxies have an average error of less than 2% (compared with simulation results) and are concluded to be robust based on the blind test results. It has also been found that to reach the maximum oil recovery using CO2-WAG, the maximum gas injection rate with the minimum water injection rate is required. However, this configuration may result in a reduction in the total CO2 stored in the reservoir.