Chemical composition and amount of produced water microorganisms of offshore oil production were investigated. An excess of the content of a number of chemicals was found. The most significant deviation is the excess of chemical oxygen demand (COD). The change in chromaticity, the presence of a specific odor and qualitative reactions to the presence of aromatic hydrocarbons indicate the presence of dissolved petroleum hydrocarbons in water. Hydrocarbons contained in reservoir waters are very toxic. Their acute toxicity for Daphnia magna was shown. In order to prevent harmful effects on the ecosystem of wastewater of this type, it is proposed to use a sorp-tion treatment method.