Abstract: In order to solve the problem of low water flooding development efficiency caused by strong reservoir heterogeneity, high water injection intensity, injected water influx and ineffective circulation in the Bohai P Oilfield, a study of in-situ CO₂ generation technology was carried out. Firstly, the optimal gas generation system was selected by evaluating gas generation efficiency. Then, the foaming agent and blocking agent were screened by the Waring-Blender method and sandpack column flow experiment. Laboratory test results showed that gas generation efficiency could reach 96.2% when the gas system was blowing agent A + gas release agent D. The optimal foaming agent system was 0.2% foaming agent 2 + 0.1% foaming agent 5. The foaming volume was 740 mL and the half-life of dissolve-out liquid could be maintained for 219 seconds. When blocking agent 1 was added in the foaming system, the plugging rate could be maintained above 90% in the sandpack column with a permeability of 2 000-10 000 mD. The in-situ CO₂ generation technology had been used in 15 injector producer pairs of the Bohai P Oilfield, resulting in the enhancement of accumulative oil recovery of 33 413 m³ by injecting 69 986 m³ of CO₂ in total, with the effective rate reaching 100% and effective period up to 5 months, which indicated that in-situ CO₂ generation technology had good applicability in Bohai P Oilfield and dissolves the problems existing in the water flood development of this field.