The Davis Strait - DCE - Nationalt Center for Miljø og Energi

10.3 Development and production activities
In contrast to the temporary activities of the exploration phase, activities
during development and production are usually long lasting, depending on
the amount of producible petroleum products and the production rate. The
activities are numerous and extensive, and the effects on the environment
can be summarised under following headings:
• solid and fluid waste materials to be disposed of
• placement of structures
• noise from facilities and transport
• emissions to air.
10.3.1 Produced water
During production several by-products and waste products are produced
that have to be disposed of in one way or another. Produced water is by far
the largest contributor in his respect from an oil field (see section 2.4).
Generally it is assessed that the environmental impacts from produced water
discharged to the sea are small due to dilution. For example, discharges during
the 5% ‘off normal time’ in Lofoten-Barents Sea been assessed not to impact
stocks of important fish species. But in the same assessment it is also
stated that the long-term effects of the release of produced water are unknown
(Rye et al. 2003). Particular concern surrounds polycyclic aromatic
hydrocarbons (PAHs), the hormone-disrupting phenols, radioactive components
and nutrients in relation to toxic concentrations, bioaccumulation, fertilisation,
etc (Rye et al. 2003).
Impacts on the marine environment from produced water can be reduced by
injecting it into wellbores. This is not always possible (STF 2008) and when it
is international standards (OSPAR) must be applied as a minimum. This
means that the oil content may not be higher than 30 mg/l. In Norway released
produced water in recent years had an average oil content of 11 mg/l
(Anon 2011a).
Nutrient concentrations can be very high in produced water (e.g. ammonia
up to 40 mg/l). When diluted these nutrients may have an ecological effect
as a fertiliser, which could impact especially the composition of primary
producers (planktonic algae) (Rivkin et al. 2000, Armsworthy et al. 2005).
Even though oil concentrations in produced water on average are low, oil
sheen may occur on the water surface where the water is discharged, especially
in calm weather. This gives reason for concern, because sheen is sufficient
to impact seabirds and together with other low concentration oil discharges,
such impacts may be significant (Fraser et al. 2006).
To test potential effects of produced water on organisms, cages with Atlantic
cod and blue mussels, respectively, were positioned at various distances (0-
5000 m) in different directions from oil platforms in Norway. In addition,
two reference locations were used, both 8000 m away from the respective
platforms. PAH tissue residues in blue mussels ranged between 0-40ng/g
ww depending on the distance to the oil rigs. PAH bile metabolites in cod
confirmed exposure to effluents, but levels were low when compared to
those found in cod from coastal waters (Hylland et al. 2008). The biological
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