Abstract: Through use of the numerical reservoir simulation which be taken in the thesis as a main way and general geological analysis as secondarily field,to study its genetic type of low permeability reservoir of fluviatile facies,the distribution law and the potential of residual oil ind ividual layer as individual layer in Chang-2 reservoirs of Tanjiaying oildom of An sai oil field.The authors think types of main residual oil contain that didn't controlled by well net,is spread to the area by water flooding and exloitation,is resorted on the top of thick oil layer,and is in terfered by in terbedding.