Assessment of the discharge of NORM to the North Sea from produced water by the Norwegian oil and gas industry

Abstract

Abstract In order to obtain a reliable estimate of the discharge of NORM (Naturally Occurring Radioactive Materials) to the North Sea from the Norwegian oil and gas industry, produced water from 41 Norwegian offshore platforms has been sampled during a five-month period from the autumn of 2003 to early 2004 and analysed for 226 Ra, 228 Ra and 210 Pb. Together with data on the volume of produced water discharged from each production platform, the total activity of radium discharged to the North Sea in 2003 has been estimated. Activity concentration of 226 Ra and 228 Ra in the samples ranged from below the detection limit (0.3–1.3 Bq l −1 ) up to 16 and 21 Bq l −1 , respectively. For 210 Pb, all results except one were below the detection limit (0.2–1.5 Bq l −1 ). For some of the platforms, short-term variations in the activity concentration were observed. The discharge of 226 Ra and 228 Ra through produced water in 2003 from the Norwegian oil and gas industry into the North Sea was estimated to be 440 GBq and 380 GBq, respectively. Dividing the total discharged activity by the total volume of produced water discharged in 2003 gives an average activity concentration of 3.3 Bq l −1 for 226 Ra and 2.8 Bq l −1 for 228 Ra in produced water from the Norwegian continental shelf.