Study on CO ₂ Miscible Flooding Front Migration Characteristics and Dynamic Sweep Law in Low Permeability Reservoir With Barrier

ABSTRACT In low‐permeability reservoirs, the development of a barrier significantly influences fluid migration and remaining oil distribution during CO 2 miscible flooding. Thus, a comprehensive study of the migration characteristics and dynamic sweep law of the CO 2 miscible flooding front in low‐permeability reservoirs with a barrier is crucial for optimizing gas flooding reservoir development design and enhancing oil recovery. Based on the geological features of a low‐permeability reservoir block in the Jilin Oilfield, a visualized two‐dimensional model with a barrier was designed and fabricated. Then, two sets of CO 2 miscible flooding experiments were carried out using different injection‐production modes. By analyzing the dynamic images and the key injection‐production parameters during the experiments, the impact of the barrier on oil–gas migration and remaining oil distribution during CO 2 miscible flooding in low‐permeability reservoirs was investigated, and the front migration characteristics and dynamic sweep law of the CO 2 miscible flooding in low‐permeability reservoirs with barrier were revealed. The results show that: (1) The combined effects of gravity differentiation and barrier significantly influence the migration of oil and gas and the distribution of remaining oil. This impact directly leads to notable differences in the migration characteristics and dynamic sweep law of the flooding front under different injection‐production modes. (2) Barrier affects CO 2 displacement through dual mechanisms of interference and obstruction. (3) In this experiment, injecting CO 2 from one side of the barrier achieved better oil displacement results than injecting from the side without a barrier. Therefore, the position of the barrier should be fully considered before actual field production, and a reasonable injection‐production scheme should be formulated accordingly to mitigate the negative impact of barriers on the oil recovery. (4) To achieve efficient reservoir development, injection‐production parameters should be monitored in real time during CO 2 flooding, and the injection‐production rates and positions should be dynamically adjusted based on the flow characteristics of gas flooding.