In the Middle East area，some carbonate reservoirs have characteristic of porous-type reservoir with few fractures and caves and low in permeability. Based on the fluid analysis on A oil reservoir in the Middle East，some experiments on oil displacement methods of enhanced oil recovery were carried out. The results show that immiscible displacement can enhance oil recovery because gas flooding can lead to oil volume expansion，viscosity decline and mobility improvement. Under the conditions of A oil reservoir，CO2 miscible displacement can be achieved while associated gas miscible displacement can’t be achieved.CO2 WAG miscible displacement is the most effective method and associated gas WAG immiscible displacement can improve oil recovery to a certain degree. CO2 WAG miscible displacement after water flooding significantly improved oil recovery by nearly 20%，but CO2 WAG miscible displacement after associated gas immiscible displacement only improved oil recovery by 2%. Under field conditions，the combination oil displacement method of gas immiscible and miscible displacement is not available；CO2 WAG miscible displacement after water flooding is suggested.