Abstract: Because of high salinity and weak acidity of the produced water in LinNan oilfield, the treated injection water brings about a series of problems, such as serious corrosion, scale formation and unqualified injection water. The technical mechanism of modification of the injection water and the relation between the water modification pH value and corrosion, sludge quantity and scaling are studied， the optimal pH value of the modified injection water is 8.20. After modified, the corrosive electric density of the water is 1/3 lower than that of original injection water, the sludge quantity is only 1/5 of that of the water which is not optimized, and the scaling decreases tremendously. Field application demonstrates the main index of the water quality reaches standard, scaling and corrosion of pipeline system and well bore lower, stimulation effectiveness of injection is getting better, and the startup pressure of injectors' decreases and the water absorption index increases, and a positive impact on development effectiveness is brought out.

Key words: LinNan Oilfield, water quality modification, pH optimization, research, application