Chemical characterization of produced water from four offshore oil production platforms in the north sea

Abstract

Samples of produced water from the offshore oil production platforms Oseberg Feltsenter, Oseberg C, Brage and Troll B were collected during the period of October 1995 to August 1996. The samples were analysed for polycyclic aromatic hydrocarbons and phenols by gas chromatography with a mass-spectrometric detector. Analysis of organic acids was done by isotachophoresis, metal determinations by atomic absorption spectrometry, and radioactivity measurements by high resolution gamma spectroscopy. The results were included in a database of chemical composition of produced water, and were then compared with data from other fields in the Norwegian sector of the North Sea using principal component analysis. The concentrations of naphthalene, phenanthrene, dibenzothiophene, and their C1-C3 alkyl homologues, and alkylated phenols show decreasing levels with increasing alkylation of the components for all fields. The results show that there is no correlation between the THC content, which today is used as emission standard for environmental regulation, and the content of the aromatic compounds, which are assumed to be the most important contributors to toxicity. Field-specific detailed chemical characterisation of produced water from each platform is necessary in predicting fate and effects of the produced water discharged to the marine environment.