Abstract: Some oil wells in Xinzhan oilfield,mainly consisting of low-permeability fissured pools,were shut in for high wa- ter cut by natural fissure.For the sake of residual oil,the study on numerical simulation with CMG software is per- formed.On the basis of fine history matching,the distribu- tion character and the generation mechanism of residual oil are analyzed.Five plans for pattern thickening and water flooding method modification are designed for tagging residu- al oil.And the development indexes of every plan are predic- ted.In comparison with the development effect of different plan,and in combination with the actual situation of the oil field,the rational plan of pattern thickening and modification is defined as that injection wells in the original pattern should be thickened by injection wells,and new and original injec- tion wells should be injected alternatively.