Sensitivity analysis of water-alternating-CO2 flooding for enhanced oil recovery in high water cut oil reservoirs

The objective of this work is to investigate the effect of operational schemes, reservoir types and development parameters on both the amount of incremental oil produced and CO2 stored in high water cut oil reservoirs during CO2 water-alternating-gas (WAG) flooding by running compositional numerical simulator.The method used is the orthogonal experimental design method to optimize operation parameters, including CO2 slug size, ratio of CO2 slug size to water slug size (WAG ratio), CO2 injection rate, and voidage replacement ratio. The Net Present Value (NPV) was used as an objective function for economic analysis. Various 3-D heterogeneous reservoir models were built to investigate the impact of reservoir types and development parameters on CO2 flooding efficiency and storage capacity.The results indicate that as compared to inverted nine-spot pattern and inverted seven-spot pattern, five-spot pattern is more suitable for CO2 WAG flooding. The earlier water injection is switched to CO2, the more benefit can be obtained. Compared with CO2 injection cost and tax credit per ton of CO2 stored, oil price is considered as the most influential economic parameter on CO2 WAG flooding.