Pilot Study on Enhanced Oil Recovery by Gravity Assisted Deoxygenated Air Flooding in N Fault Block

In order to solve the problem of poor water flooding development effect of extra-low permeability reservoir in Dagang Oilfield, N fault block is selected to carry out continuous gas injection and intermittent gas injection test. Before the test, in order to optimize the test parameters, experiments are conducted on the oxygen concentration of injected air, injection pressure, and enhanced oil recovery. The design is to inject deoxygenated air with oxygen concentration of 8%, and the injection pressure is 35 MPa. The test results show that the injection capacity of the deoxygenated air is prominent and the effect of increasing production is obvious. In the continuous gas injection stage, the oil production is high, but the gas breakthrough is fast, and the production of well group decreases greatly. The production of intermittent gas injection stage is slightly low, but the production decline of well group is small. At the same gas injection rate, the cumulative oil production of intermittent gas injection well group is higher than that of continuous gas injection well group. Field tests indicate a recovery of 14.2%, which improves recovery by 9.5 percentage points. The experimental results show that the technology of deoxygenated air flooding is feasible for improving oil recovery in extra-low permeability reservoirs, and it has great significance for popularization.