Abstract: It is of great importance to further study flooding mechanism if the oil saturation and the distribution in reservoir rocks are know. By using industrial computerized tomography, the paper presents a method to measure the density difference of saturation distribution after the displacement of oil - bearing cores.Theprocedure ison the same sectionof a core sample , to do scanning to dry sample, saturated sample and displaced sample respectively, then the corresponding section image is rebuilt,and the gray scale value is measured and density value is calculated. Based on the above values, saturation and its distribution can be calculated by Density Difference Method. The authors have conducted a measurement to a rock sample from certain oil field by an industrial computerized tomography CD - 300BG withγ- ray. The result indicates that the CT density difference method is effective to measure the saturation distribution. Compared with ordinary flooding methods, it is faster , more accurate , no damage to rock sample and can simulateformation condition. Therefore , it isa new effective methodforoilfield

Key words: reservoir, core, core testing, saturation distribution, density difference