Experimental study of CO2 storage in water-flooded oilfields

CO2 is the main source of greenhouse emission, and the environment problem caused by greenhouse effect has drawn worldwide attention. In most oilfields in China, a method of waterflooding is usually used to enhance oil recovery, which is favorable to carry out CO2 injection study. The CO2 injection in the water-flooded oilfields can not only store CO2, but also enhance the oil recovery. In this article, the core-flooding tests with refined oil were conducted to investigate CO2 displacement characteristic in water-saturated formation under different injection rate and water-flooded oil reservoir under different formation pressure and oil saturation, then the CO2 storage capacity was calculated. The testing result shows that the displacement efficiency increases with the rise of the CO2 injection rate, and the CO2 injection can enhance the oil recovery about 15% OOIP under the experimental condition. When injecting CO2 after the waterflooding, the CO2 storage capacity increases as the rise of the formation pressure. The core-flooding tests also indicate that when the initial oil saturation of reservoir prior CO2 injection is higher, the oil recovery will be higher when injecting the same pore volume (PV) of CO2, and the CO2 storage capacity will be larger.