An experimental study of combined foam/surfactant polymer (SP) flooding for carbone dioxide-enhanced oil recovery (CO2-EOR)

To better address the issue of viscous fingering and gravity segregation confronted in CO2 flooding, a novel EOR method which coupled the SP flooding with the CO2 foam flooding was presented. Its displacement performance was systematically evaluated and compared with the other two injections modes (i.e. direct foam flooding and CO2/SP flooding) which applied the same amount of the gas and chemicals as the proposed mode. It had been found, if the injection pressure enabled the oil/CO2 miscibility to occur, the foam/SP flooding was endowed with the highest blockage and lowest water cut. Moreover, its oil recovery factor was 5.8% and 12.6% greater than that of direct foam CO2/SP flooding respectively; on the other hand, if the injection pressure was below the minimum miscibility pressure (MMP), the direct foam flooding and the SP flooding displayed. comparable water cut and oil recovery factor. Although the foam/SP flooding still recovered the most crude oil, it was only 3.7% and 6.8% higher than that of the direct foam and SP flooding respectively, indicating the less evident displacement advantage. It was believed that the proposed method possessed huge EOR potential, especially in the reservoir whose pressure was well above the MMP.