Abstract: in this paper, a numerical model for the cylic water flooding in the heterogeneous reservoir is founded by studing it‘s seepage mechanism. The store room for the residual oil seepage in microcosmic is named the second seep sys-tem. Two series of block system lapped in space is applied to describe theheterogeneous of reservoir.The corse of water displacing oil is simulated with this model, and some factors that effect the cyclic flooding, such as the geo-logical and manual are analysised by contrsting. It is suggested to make policy and optimize manual means that the mechanism of water displacing oil in the course of cyclic flooding and the best conditions and manual means in reservoir.

Key words: Heterogeneous reservoir, Cyclic injection, Numerical simulation, Mechanism, Seepage evaluation