Displacement experiments of oil by water of Chang-6 and Chang-2 reservoir models in Jing'an Oilfields were made. The results indicate that their final oil displacement efficiency differ very little though they have differences in physical properties

and there is greater increase in oil displacement efficiency of Chang-6 reservoir (25.79%) than that of Chang-2 reservoir (4.32%) after water-free period. The major factors affecting their oil displacement efficiencyare the pore structure

the wettability

and pressure increasing way of injected water of the reservoirs.