Metocean conditions
The
region is characterised by its complex bathymetry and oceanography. Wind and
wave conditions are severe, reflecting exposure to the Atlantic Ocean; storm
waves can include both long-period swells and very steep-crested large waves.
Currents are both energetic and complicated (spatially & temporally). Together,
these factors present unique challenges.
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This satellite
image uses sea surface temperatures to reveal warm and cold eddies in
the Faroe-Shetland channel.
These form
because of instabilities between the main influx of Atlantic water on
the UK side (the "slope current") and southward moving water
on the Faroese side of the FSC.
Below these
water masses lies a much colder, heavier water body moving generally southward.
Linking
the Atlantic and Arctic Oceans in this way, the FSC plays a key role in
the global ocean circulation.
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 2:
Satellite image (AVHRR) showing sea surface temperature and eddy and
meander features (courtesy of RSDAS)
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Description
of currents West of Shetland
Commissioned
by BP, Metoc prepared a short note describing the current conditions in the
West of Shetland oil & gas province (Ref
BN977, Aug 2002). This note:
 |
sets
West of Shetland in the context of global ocean circulation |
|
explains
why currents in the region are complex and how they depend on bathymet
ry |
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describes
the different water masses in the upper and lower layers |
|
highlights
the importance of position in the Faroe-Shetland Channel |
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describes
the main current processes – regionally and smaller-scale |
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gives
indicative values of extreme current speeds. |
Development
of Metocean Design Basis
Grant,
Dyer & Leggett (OTC paper 7685, 1995) discuss
the development of a metocean design basis for West of Shetland developments
in quadrant 204. The development location is in a water depth range of 375
m to 850 m, with the first field, “Foinaven”, in around 450 – 500 m. The paper
inludes a brief comparison of typical metocean design criteria for the area
around Foinaven with those at BP’s Magnus field which in a water depth of 185
m is the deepest development on the continental shelf in the UK sector.
Severity
Compared against Other Regions
This
diagram puts the metocean conditions of the Northwest Approaches in a global
perspective by comparing its key metocean criteria against those of other major
deepwater oil and gas provinces. (click
this link to see an enlarged version).
