Abstract: Aiming at the complex well occurrence distribution problem at the late period of oilfield development,based on the analysis of reservoir geological anomalies and inhomogeneous,by using the geological and development data of oil reservoirs in western slope belt of Dongpu sag,tree-type infilling and hydrocarbon accumulation pattern have been put forward.The tree-type hydrocarbon accumulation pattern can be explained as the phenomenon of water layers at the top and oil layers at the bottom,and it is good for searching for hidden reservoirs.Hydrocarbon can be filled,mixed andenriched in a certain channel and there is no hydrocarbon accumulation outside the channel.H-19 block of western slope belt of Dongpu sag has 8 faults and 7 complex faulted-blocks.On a large scale,oil and gas reservoirs are accumulated in the structural high part.On a small scale,oil and gas distribution is more complicated.There are more abnormal areas and negative anomaly areas among the adjacent region of the same faulted-block.The tree type accumulation pattern may result in abnormal distribution of oil and gas,and it is more serious at the late reservoir development stage and the difficulty for identifying oil-water layers can be increased.The common identification method has the characteristic of reservoir inclusion.