Large amounts of water are produced during the production of crude oil and natural gas. This water has to be analyzed to realize the correct geological formation. In this work. an extensive analysis of oil field water delivered from Gulf of Suez was carried out to determine the composition of the precipitate formed before starting waterflood operation. Cation and anions are the main interest of this analysis and are carried out using ion chromatography (IC). The data of water analysis have been used as an input data for computer software program. The scale precipitation processes in the bulk solution as well as the tendency rate and inhibitor effectiveness have been determined using jar test methods. The data arising from jar test are compared with the output of the software program to evaluate and quantify the scale precipitation. Also. the mixing waters are analyzed after precipitation to determine the consumed calcium and sulfate ions in presence and absence of inhibitor. It was found that mixing of the injection water and formation water leads to calcium carbonate and barium sulfate scaling at 60% formation water in absence of scale inhibitor. (C) 2009 Elsevier B.V. All rights reserved.