Environmental effect of produced water from North Sea oil operations

Abstract

From the Abstract: “Produced water from North Sea oil reservoirs contains substantial amounts (about lg I-I) of non-hydrocarbon organic matter, largely as salts of acetic, propionic and butyric acids, as well as some 20-40 mg I-1of dissolved hydrocarbons such as benzene, toluene and xylene. The non-hydrocarbon components originate in water in the oil-bearing formation. All of the organic matter can be accounted for, within analytical accuracy. The water also contains some 20–30 mg I-1 of ammoniacal nitrogen and a number of inorganic components.

At peak water production from production installations in the North Sea some 1-2 105 105 tonnes yr-1 of organic acids will be discharged in the U.K. sector of the North Sea. The ready biodegradability of the organic constituents and the low toxicity of produced water have been confirmed by direct measurement; acute toxicity is unlikely at dilutions of greater than 100 fold. Dispersion has been modelled and tested in the laboratory indicating some 1000 fold dilution within less than 50 m of the discharge. The laboratory studies are supported by field observations. Any direct deleterious effects are limited to the immediate vicinity of the discharge (within a few tens of metres).