Low Salinity and Immiscible CO2 Combined Flooding For Sandstone Reservoirs: Low Salinity-Alternating- CO2 Flooding (LS-CO2 WAG)

Abstract

Summary Low salinity (LS) water flooding and CO2 flooding are two new combination floods coupled due to the vital role of both in methods for increasing oil recovery. LS water was examined by many laboratory and field works, and it showed an impressive result in enhancing oil recovery. CO2 was tested on increasing oil recovery, and the oil recovery increased by improved wettability alteration effect towards more water-wet and interfacial tension reduction. Although CO2 showed an improvement in oil recovery, the density difference between CO2 and oil resulted in gravity override and channeling problems. LS water alternating CO2 flood gathers the benefits of LS itself to improve sweep efficiency by CO2, prevent the CO2 problems mentioned earlier, and capture the CO2 from the atmosphere. Furthermore, miscible CO2 flooding can reduce oil viscosity and trigger oil swelling. The laboratory experiments of all scenarios showed an incremental oil recovery, but the optimum scenario was the huff and puff-LS water-CO2-LS water scenario with additional oil recovery of 20.65% of OOIP. The three-hours huffing mobilized a new bank of oil, while the shorter LS water-CO2 cycles were the second optimum with incremental oil recovery 17.95% of the OOIP. This combination technology can solve the CO2 flooding problems and support CO2 by LS water, which in itself can increase oil recovery by altering the wettability towards more water-wet.