Research on the Optimization of CO2 Flooding Parameters in the F Ultra-Low Permeability Oil Reservoir in Region X

The F oil reservoir is a low-porosity and ultra-low permeability oil reservoir. The natural productivity of oil wells is low, and large-scale fracturing completion is required to achieve effective production deployment. However, after production deployment, the production decline is rapid, and the cost of repeated fracturing for energy replenishment is high, resulting in a high proportion of low-efficiency wells in the development area and a low recovery rate. There is an urgent need to explore effective enhanced oil recovery (EOR) technologies. CO2 flooding has a good application effect in ultra-low permeability reservoirs and is an important method for improving oil recovery. It can continuously and stably maintain the formation energy and further enhance the oil recovery rate of ultra-low permeability oil reservoirs. Therefore, starting from the geological model of the F oil reservoir in Region X, this paper establishes a three-dimensional geological model of the reservoir and uses the numerical simulation method to optimize the key parameters of CO2 flooding development. The results show that the more the gas injection volume, the higher the daily oil production and the cumulative oil production. However, in the initial stage (the first two years), it is still in the late stage of water flooding. The larger the gas injection volume, the greater the liquid production, and the water cut also increases rapidly. In the later stage, the water cut drops rapidly, and the oil production increases significantly. The reasonable injection rate is 8–10 t/d, the optimal injection volume is 1.6 HCPV, the optimal injection pressure is 28 MPa, and the gas-water alternate injection with a gas-water ratio of 1:2 can maximize the development benefits of the oil reservoir.