Study and Pilot Test of Air Foam Flooding in High Water Cut and Fault Block Reservoirs

Abstract

Aiming at the complex fault block reservoir with high water cut and high recovery percent, the study and pilot test of air foam flooding to further improve the oil recovery was carried out. A coupled air-foam system with increased seepage resistance and reduced interfacial tension was developed and applied in a pilot test. The laboratory evaluation shows that the new air-foam system could improve oil recovery by 33.2%, and the seepage resistance factor could reach more than 60. Based on the characteristics of air foam system, the technology of gas-liquid mixed injection from the surface was developed. Meanwhile, the oxygen content of the injection air could be reduced to below 10% with the application of oxygen reduction process through changing the adsorption pressure, which made it possible to overcome the explosion risk of the mixed gas. By using the injection tube with epoxy resin coating, we could effectively reduce the air permeability and slow down the column corrosion rate. The pilot test shows that the foam could be generated efficiently, and the injection pressure could increase by 4.3 MPa. The oxygen content of the injected air was 8–9%, whereas, during the whole test, none oxygen was produced from the production wells, which indicates that our air injection technology was safe and controllable. With the injection of the air-foam system, the single well in the pilot site has obtained obvious results of increasing oil and reducing water, and the water cut is reduced by up to 10%. It was predicted that this new air-foam system will eventually improve the oil recovery by 12.6%. The results of the pilot indicate that air foaming flooding is effective in the complex fault block reservoir, and this exploration of its implementation mode and related supporting process is of great significance for further test and application of this technology.