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

tings/well and in total 6,000 tons of drilling mud. Energy consumption is
very high during drilling, resulting in emissions of combustion gases such as
CO2, SO2 and NOx.
High levels of underwater noise are generated during drilling, mainly from
the propellers, which secure the position of floating rigs. This noise has the
potential to disturb marine mammals and acoustically sensitive fish (Schick
& Urban 2000, Popper et al. 2004).
2.3 Drilling mud and cuttings
Drilling muds are used to optimise drilling operations. Muds were previously
oil-based (OBM), but due to the toxicity, they have now been replaced
mainly by water-based muds (WBM) or for drilling under certain difficult
conditions by synthetic-based muds (SBM). The drilling results in a mixture
of drilling mud fluids and solids, rock fragments (cuttings) and certain
chemicals. Cuttings and mud have usually been deposited on the sea floor
surrounding drill sites, resulting impacts on the benthic communities.
2.4 Appraisal drilling
If promising amounts of oil and gas are confirmed, field appraisal is used to
establish the size of the field and the most appropriate production method,
in order to assess whether the field is commercial. Appraisal may take several
years to complete. Several appraisal wells are drilled to confirm the size
and structure of the field, and well logging (analysis) provides data on the
hydrocarbon bearing rocks. Well testing provides hydrocarbon samples and
information on flow rate, temperatures and pressures. If appraisal confirms
a commercial reservoir, the operator may then proceed to development.
2.5 Other exploration activities
One activity that may have environmental impact during the exploration
phase is helicopter transport, which is associated with strong noise and can
scare birds and marine mammals over a range of many kilometres.
Well testing takes place when a well has been drilled and the presence of
hydrocarbons and the potential for production is to be evaluated. The testing
activities normally imply the use and release to the sea of different chemicals,
occasionally including radioactive compounds.
2.6 Development and production
Field development also includes seismic surveys and extensive drilling activities
(delineation wells, injection wells, etc), and drilling will take place
until the field is fully developed. An oil development feasibility study in the
sea west of Disko Island (north of the assessment area) assessed the most
likely scenario to be a subsea well and gathering system tied back to a production
facility either in shallower water established on a gravity-based
structure (GBS) or onshore (APA 2003). From the production facility crude
oil subsequently has to be transported by shuttle tankers to a trans-shipment
terminal, most likely in eastern Canada.
Environmental concerns during the development will mainly be related to
seismic surveys, to drilling, to the construction of the facilities on the seabed
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