Abstract: The injected water samples offered by SZ36-1 oil field are seawater, sewage and formation water. The scale produced by the injection water is one of the important factors that impac jection of flooding wells and developing effect in the oil field. Analysis results of water show that the concentration of SO^2-₄is as high as 3670 mg/L in seawater, which requires special attention to the concentration of Ba²⁺in source water that mixed with seawater during flooding in order to avoid generating BaSO₄scale. In addition, there are some HCO^-₃ions in the three kinds of source water, so it is essential to consider the fact that the changing of temperature breaks the balance of water system and generates CaCO3scale. The tendency of scaling of the mixed samples of three kinds of source water is studied under the formation temperature (60℃) and the normal temperature (20℃) by the perpendicular method. Results show that the maximums of scale of the mixed samples of three kinds of
source water are very different (they are 139 mg/L and 12 mg/L) under the different temperatures. At the same time, the optimal and the worst mixture ratio of the mixed sample of three kinds of source water are obtained respectively. It provides a reliable basis for injecting mixed formation water, sewage and seawater of the oil field.

Key words: source water, mixed injection, scaling, temperature influence, mixture ratio