Abstract: Property balance calculation is an important reviewing method for the data of crude oil assay. There is always deviation between test datum and calculated value during the balance calculation of crude oil properties in practice. The allowable relative deviations for some balance calculations of crude oil properties are concluded through studying huge amount of crude oil assay data by statistical method, and these empirical values could be used as one of the important criterions for data review in crude oil assay.

Key words: crude oil assay, property balance calculation, allowable deviation