Abstract: Nowadays，most oilfields in the world have come into their mature stage with a middle or high water cut.In this stage，much moveable oil can not be exploited yet.So petroleum engineers expect the oil recovery can be improved by studying on the reservoir heterogeneity.The heterogeneity of oilfield A is studied in this paper by using statistics and Lorentz curve.The reservoir heterogeneity includes plane heterogeneity，internal heterogeneity in the target layers and the heterogeneity between target layers.Research indicates that the plane heterogeneity and the heterogeneity between target layers in oilfield A are both serious and the internal heterogeneity is moderate.This research also makes a contrast of these two methods，it is recognized that the method of Lorentz curve is easier to determine the degree of the reservoir heterogeneity than the method of statistics.And moreover，the method of Lorentz curve is a quantitative approach to study the reservoir heterogeneity.

Key words: reservoir heterogeneity, statistics, Lorentz curve, variation coefficient, dart coefficient