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

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from the particles in the water-based mud have been observed on fish and
bivalves under laboratory conditions (Bechmann et al. 2006).
Mitigation of impacts from the release of drilling mud and cuttings
The best way of mitigating impacts from drilling mud and cuttings in the
marine environment is to bring these to land or re-inject the material into
wellbores. This, however, creates other environmental impacts such as increased
emission of greenhouse gasses from the transport and pumping and
problems with treatment or re-use on land (SFT 2008). These have then to be
balanced against the impacts on the water column and on the seafloor. A recent
report (SFT 2008) has recommended that general zero-discharge requirements
relating to water-based drill cuttings and mud are not introduced
in Norway.
It is generally assessed that impacts from water-based muds are limited,
which is why they are usually released to the marine environment when the
drilling is over. However, as part of the post-drill environmental monitoring
that licence holders off the coast of Greenland are required to perform during
exploration drilling, particle transport in relation to drilling mud has to
be modelled and sediment traps have to be set up to measure the potential
spatial distribution of these particles. Impacts can be further reduced by application
of environmentally friendly drilling chemicals, such as those classified
by OSPAR (HOCNF) as ‘green’/PLONOR (Pose Little Or No Risk to the
Environment) or ‘yellow’. However, in general these chemicals have not yet
been evaluated under Arctic conditions with regard to degradation and toxicity,
and all chemicals to be discharged should be assessed and evaluated
before they are approved for release.
In Norway, releases to the marine environment of environmentally hazardous
substances (‘red’ and ‘black’ chemicals) have been reduced by 99% in
the period 1997-2007, through application of the international standards,
BAT and BEP (SFT 2008). In Greenland the use of ‘black’ chemicals is not allowed
and specific permission is required for the use of ‘red’ chemicals.
Impacts from oil-contaminated drill cuttings should be mitigated by keeping
them on board for deposition or cleaning on land.
Conclusion on discharges from exploration drilling
Within the assessment area only very local effects on the benthos are to be
expected from discharging the water-based muds (WBM) during exploration
drilling (Table 10.1.2). For this reason, the potential impact on benthic feeders,
such as king eider, walrus and bearded seal, will probably not be significant.
However, baseline studies and environmental monitoring should be
conducted at all drill sites to document spatial and temporal effects, and to
assess if there are unique communities or species that could be harmed.
10.2 Appraisal activities
Activities during the appraisal phase are similar to exploration activities (see
above) and the impacts are the same. However, there is an increased risk of
cumulative impacts as the phase usually takes place over several years.