Acid-resistant Foamer Used to Control Gas Breakthrough for CO2 Drive Reservoir

Abstract Due to the prone gas breakthrough in CO2 immiscible flooding, the development effect was poor. In order to block off gas breakthrough channels, improve gas injection/production profile, and increase sweep volume & efficiency, two different acid-resistant and oil-resistant foam systems were developed according to reservoir characteristics and fluid features in Daqing peripheral oilfield. The foam system swelled 4times, the half-life was 83h, and core resistance coefficient was 120 under the condition of PH=3 and 60% oil saturation. Filed test results showed that the systems can effectively block off gas channels, decrease inefficient circulation, increase CO2 sweep volume & efficiency as well as displacement efficiency. The tested well gas injection pressure rose by 3.5MPa after resuming injection. Dominant injection direction changed obviously and gas sweep area increased enormously. Connected wells’ gas oil ratio decreased with an average valid period of 11 months and cumulative oil increment of 467t. This gas breakthrough blocking off technology is suitable for gas flooding development of Daqing peripheral oilfields which have ultra-low permeability, and has the advantages of high efficiency and low costs. It provides a sound technique support for gas flooding development.