For CO ₂ flooding in heterogeneous reservoir, gas channeling of CO ₂ is easy and premature to happen along the high permeable layers, which leads to low recovery efficiency of CO ₂ flooding and low-permeability reservoir is difficultly produced, optimal selection of different CO ₂ injection modes was developed in laboratory test. The influence of slug size, foam-gas ratio and surfactant-gas ratio on the optimal injection mode was also studied. The results show that foam-gas alternative flooding is an effective practice to tackle serious interlayer contradiction and prevent early gas break-though, leading to a high oil recovery. The best parameters for FAG are as following: slug size (0.4 PV), foam-gas ratio (1∶1), surfactant-gas ratio (1∶1).

The influence of certain parameters on foam flooding in heterogeneous formations was researched using paralleled core experiment.The results show that the lowpermeability formations attribute more to the increment of oil recovery in foam flooding,while the increment of oil recovery of high permeability formations is small;Considering the oil recovery and economic benefit,the injection volume of foam is supposed to be 0.3PV~0.5PV;the permeability max-min ratio should be smaller than 15 in foam flooding,and when the permeability max-min ratio was 10,the increase amplitude of oil recovery reaches maximum.The increase amplitude raises first and then declines along with the increase of water cut,when the water cut was 80% ~90%,the oil recovery reaches maximum.The continuous injection exhibits better performance than the slugging injection and the method of alternative injection of gas and liquid between foam injecting.

The foaming behavior and its influence of an anionic sulphonate foaming agent(FA220) were researched.It was found that both of the foaming volume and half-time of foam reach the highest point when the concentration of foaming agent is 0.6%;FA220 has a good ability of resistance to Mg²⁺ ,NaCl and Ca²⁺ bring some neglect impact on the stability of foam and very little impact on the foaming volume; the addition of polymer improves the foam system stability and decreases the foaming volume,the foaming volume and half-time of foam make better result when the concentration of polymer was between 0.3~0.8g/L;oil has obvious defoaming effect,the defoaming effect become stronger with the increase of oil saturation.

Foam fluid has good property, widely used in petroleum engineering. Density of foam fluid is very important in site application. Device designing used to measure density of foam fluid was introduced under underhole situation. Method to quantitatively determine the density-pressure-temperature relation of the foam fluid was also put forward. The relations between the density of the foam fluid and the pressure and temperature were measured using the method. Experiential formulas calculating density of foam fluid were gained through regression method. The results of measurement and conventional calculation were compared. It shows that density of foam fluid increases with pressure increases, and decreases with temperature increases. The larger the ratio of gas and liquid weight in foam fluid is, the better the condensability of foam fluid is. The measured density of foam fluid is always less than that of calculated by conventional method. Difference lies in 1.45 %to 11.31%. The reason is that repellent force of surfactant ions has not been considered when calculating by conventional method. The regressed formulas have good accordance with the experimental data. The research conclusions can direct foam fluid application in oil field.