A critical review of the CO2 huff 'n' puff process for enhanced heavy oil recovery

Experimental studies on the CO2 huff 'n' puff process indicate that the process applied in the heavy oil reservoir is successful and can be carried out with an oil viscosity up to 28,646 mPa·s and a reservoir permeability up to 24,200 mD. In pilot tests in the field, economical CO2 huff 'n' puff processes have been applied in the heavy oil reservoirs with an oil gravity as low as 4 °API, a reservoir depth as high as 1985 m, and a pay zone as low as 12.2 m. Specifically, CO2 utilization can be as low as 4.2 Mscf/Stb. Numerical simulation studies can gain very good simulation results on both experimental and pilot tests studies. However, mathematical models have seldom been published on CO2 huff 'n' puff processes in heavy oil reservoirs.