The Experimental Studies On The Relative Permeability Of CO₂ Flooding In Low-permeability Reservoir

In low permeability reservoirs,to a great extent, the oil displacement of gas injection production depends on displacement pressure. Mixed phase flooding occurres only when displacement pressure is higher than minimum miscibility pressure.In the enhancing oil recovery by gas injection development,a few methods determining minimum miscibility pressure have been used in China,such as straws experimental method and empirical formula method. On the basis of minimum miscibility pressure prediction by empirical formula, the interface of oil and CO2 under different pressure was observed by a high pressure window to determine the minimum miscibility pressure of different oil and CO2. The effect of oil property on minimum miscibility pressure was compared. Experiments show that the minimum miscibility pressure between oil and CO2 increases with the increase of viscosity and density of oil used. The viscosity and density of oil has some effect on minimum miscibility pressure. There are great difference between the minimum miscibility pressure determined by empirical formula and experimental measurements.According to both gas–water and gas-oil relative permeability measurement,this paper get the changing relation between gas-water and gas-oil relative permeability and gas injection pressure.When cores permeability are similar,this paper get a lot gas-water relative permeability curve that shapes are resemble and their characteristic value's difference for core structure inside.Foe those cores with the same permeability ,under different injection pressure,gas-water relative permeability curve changes in similar trend.With injection pressure increasing,gas relative permeability changing speed enhances.At the same time ,gas-water relative permeability come to the same value in less time and higher water saturation.Under different injection pressure,in a long time ,oil relative permeability reduces at large amplitude,but gas relative permeability increases not obvious.If gas injection pressure is higher ,the last gas relative permeability would be increased.