Abstract: Aiming at the following problems in the ultra-low permeability reservoir in Daqing external field, such as big residual potential, poor infilling effect, low oil recovery ratio of water flooding, the CO2 flooding technology of the ultra-low permeability reservoir is put forward. Through the slim tube experiment and the CO2 displacement experiment of natural core, the minim miscibility pressure of CO2 and oil of Gaotaizi Oilfield is obtained. The displacement effects of CO2 flooding on ultra-low permeability reservoir are evaluated. Laboratory study results show that CO2 flooding can be applied in Gaotaizi reservoir, and good displacement effects can be obtained. When the air permeability of natural core is 0.51 mD, the CO2 flooding can enhance oil recovery for more than 8 percentages after water flooding. It is feasible to carry out CO2 flooding in ultra-low permeability reservoir.

Key words: ultra-low permeability reservoir, CO2 flooding, minimum miscibility pressure, displacement experiment, Daqing Oilfield