Abstract: In the characterization of fault-blocked Machang oilfield,nine scale reservoir architectures were founded,of which the fifth and sixth order became the main subjects for characterization in the study.With the fifth order as the mapping unit,the reservoir structural model was established.According to re-servoir heterogeneity,eight types of water injection patterns were identified.The high residual oil areas were determined through injecting-water volume analysis.The residual oil belonged to four patterns as following:oil not controlled by the production well-net,oil remained for architecture element contacting,oil between two injection wells and oil remained for injection interfering.The residual oil appraisal indicated that the reservoirs were well developed,and it is difficult to maintain their production as usual.