Abstract: The method of dissolving CO₂ in water to form carbonated(CO₂-saturated)water and then injecting it into the reservoir can overcome CO₂ high mobility and gravitational segregation,improving crude oil properties and increasing recovery.However,the effects of different operational parameters on carbonated water flooding and CO₂ storage remain unclear.Therefore,numerical simulation was performed to study how different development schemes,CO₂ molar concentrations in carbonated water,and reservoir permeabilities affects carbonated water flooding performance and CO₂ sequestration.Results show that after reservoir depletion,switching to water flooding and alternating water-gas flooding yielded oil recoveries of 45.3% and 53.5% respectively.Switching to CO₂ flooding increases recovery to 63.7%,but CO₂ storage is only 31.9% due to gas channeling.In contrast,switching to carbonated water flooding achieved 58.2% recovery oil factor(between that of water and CO₂ floodings)with CO₂ storage of 44.0%.Higher CO₂ concentration in carbonated water significantly improved recovery:high CO₂ concentrations improved oil-water flow properties and accelerated CO₂ diffusion into the oil phase,markedly enhancing oil rheology and oil recovery.Furthermore,carbonated water flooding effectively increases recovery in reservoirs of different permeabilities,while reducing CO₂ channeling and enhancing CO₂ sequestration.Carbonated water flooding is therefore an effective technique for improving oil recovery and achieving CO₂ storage,with important implications for future oil-gas development and carbon sequestration.

Key words: carbonated water flooding, enhanced recovery, CO₂ sequestration, numerical simulation