Simulation Study on Optimizing Water-Alternating-Gas Carbon Dioxide (WAG-CO2) Injection Parameters for Reducing Asphaltene Precipitation in Light Oil

Water-alternating-gas (WAG) is a popular enhanced oil recovery (EOR) method widely practiced in maximizing residual oil production. However, asphaltene precipitation during water-alternating-gas carbon dioxide (WAG-CO2) injection is identified to be problematic in terms of reservoir flow assurance in light oils. Optimization of WAG process requires comprehensive understanding in WAG ratio, WAG cycle time and water injection rate. The simulation study using Eclipse 300 is suggested to perform optimization study on these WAG parameters during WAG-CO2 injection in reducing the deposited asphaltene. The optimized WAG model in considering the proposed WAG parameters is aimed to be acquired in WAG-CO2 process to minimize asphaltene precipitation and promoting more hydrocarbon production. A synthetic reservoir model with pre-defined reservoir properties and asphaltene description is prior to set up before generating two base models in further investigating the impact of the WAG parameters on oil recovery. The base models are WAG model with asphaltene and without asphaltene content. Each parameter is generated with a few options to obtain the best value during optimization phase. Field Oil Production Total (FOPT) is the output of simulation study, representing the recovery performance of WAG process in light oils under different scenarios. WAG ratio of 1 to 1, WAG cycle time of one month and water injection rate of 10000 bbl/day are the best recorded value for the WAG parameters. Higher value of each parameter is not always proportional to the oil can be produced from the reservoir. Using simulation study, WAG model without asphaltene content performs better in acquiring higher oil production than WAG model with asphaltene. It is related to the pore throat blockage of asphaltene in causing permeability reduction of reservoir when miscible carbon dioxide gas injection destroys the stability of asphaltene-resin micelles