Environmental targets offshore should include radioactivity

16 January 2009

Radioactivity should be included in the goal of zero discharges of oil and environmentally hazardous substances to sea from the petroleum activities. Measures should be considered to prevent discharges of produced water and cuttings/drilling fluid from certain oil and gas fields, but no new general requirements should be introduced.

Environmental targets offshore should include radioactivity

This is the conclusion of the Norwegian Pollution Control Authority (SFT), the Norwegian Petroleum Directorate (NPD) and the Norwegian Radiation Protection Authority (NRPA). On assignment from the Ministry of the Environment and the Ministry of Petroleum and Energy, the three agencies have considered the need for new requirements for discharges to sea from the petroleum activities in the North Sea and the Norwegian Sea.

"The petroleum activities have achieved substantial environmental improvements. Discharges of environmentally hazardous chemical additives from the Norwegian shelf have been reduced by more than 99% over the last ten years. Work is still being done to replace the remaining environmentally hazardous substances," say SFT director general Ellen Hambro, NPD director general Bente Nyland and NRPA director general Ole Harbitz.

The petroleum activities account for 3% of the national discharges of environmentally hazardous substances to sea. The largest operational discharges from oil and gas production offshore are now linked to produced water, which contains small amounts of naturally occurring substances and radioactive substances that leak out of the bedrock. So far, there are no proven direct effects of these discharges on vulnerable resources.

Environmental monitoring shows that cod and mussels placed in cages directly in the discharge stream assimilate substances from produced water, but it has proven impossible to demonstrate that such exposure has an impact on individual fish or stocks. Continued research will evaluate potential long-term effects.

Estimates based on figures from the oil companies indicate a potential cost in the order of NOK 46 billion to prevent discharges to sea from all fields on the Norwegian shelf. This includes costs associated with increased emissions to air.

"The high costs, seen in light of the fact that there are no proven effects on the environment, are the basis for why we do not recommend introducing new general requirements for injection of produced water offshore. However, requirements for specific measures should be considered on a field-by-field basis," said SFT director general Ellen Hambro, NPD director general Bente Nyland and NRPA director general Ole Harbitz.

Norway has entered into international agreements which entail a commitment to prevent radioactive pollution of the sea. So far, no direct effects have been proven from radioactive substances that can be attributed to discharges of produced water on the Norwegian shelf. Nevertheless, we do not know enough about the long-term effects, and further research is required to determine whether radioactivity in produced water can result in such effects.

For this reason, the three agencies recommend that radioactivity be included in the goal of zero discharges of oil and environmentally hazardous substances to sea from the petroleum activities. New evaluations should be made regarding injection of produced water on the Troll B and C fields, which represent about 40%of the radioactive discharges offshore.

Around 82 000 tonnes of cuttings and drilling fluid from the Norwegian shelf were sent to land for disposal in 2007, while discharges to sea amounted to around 286 000 tonnes. The SFT, the NPD and the NRPA estimate that the costs of sending all drilling fluid and cuttings to land would be considerable. Costs associated with increased landfill capacity on land have not been included, but will presumably be very high.

Discharges of cuttings and water-based drilling fluid result in a physical build-up of sludge on the seabed, but the effects are limited both in area and duration. A requirement that entails sending all cuttings and drilling fluid from the Norwegian shelf to land would result in a huge need for new landfill capacity on land, and thus also new environmental challenges. Sending water-based drilling waste to land will also result in increased emissions to air.

Therefore, the three agencies do not recommend a general requirement for zero discharges of cuttings and drilling fluid on the Norwegian shelf. However, a requirement for alternative handling should be considered in areas with particularly vulnerable benthic fauna.