In this work, Parallel Factor Analysis (PARAFAC) was used to assess the composition of produced water in 8 oil wells, using their levels of salinity, calcium, magnesium, strontium, barium and sulphate (mg/L), collected during the years 2004 and 2005. This method allowed the identification of tracers for seawater and formation water, as well as identification of standards related to seasonality. The method indicates that the variables salinity, calcium and strontium are associated with formation water, while magnesium and sulphate are associated with water injection. These variables may be used as tracers to distinguish seawater, used as injection water, and formation water, and can be very useful to evaluate the produced water composition. Seasonality aspects are associated with the variation in the levels of sulphate and magnesium, which tend to increase over time while the levels of barium usually decrease.Chemical patterns related to the original reservoirs of each oil well, called A, B and C, also were observed. Samples collected in reservoir B presented the lowest salinity, calcium, strontium and barium levels and the highest magnesium and sulphate levels, while samples from reservoir A showed intermediate levels for the same variables. 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