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Slick behaviour

Spilled oil extended offshore from Carmarthen Bay to Saint David’s Head. Patches of sheen were reported as far away as Lundy Island. During tghe first few days of March, weather conditions were such that oil was easily kept ashore.
Oil leaked from the bottom of the tanks that had been holed. Oil tended to leak most with tidal movements and particularly when the tide was ebbing. Consequently, the slick looked like a string of smaller slicks all of which were produced at low tide.

Patches were reported from time to time over a 200 kilometre stretch of coastline but thick slicks were essentially reported in Tenby Bay, in the western reaches of Carmarthen Bay and Freshwater Bay. Milford Haven Bay was also oiled over a distance of about 20 kilometres. Tar balls were reported as far away as the Irish coast but there was a high degree of uncertainty as to their origin.
Official observers reported that not much oil had stuck to exposed shorelines located from the entrance of Milford Haven Bay to Carmarthen Bay. According to AEA (Atomic Energy Agency) Technology, mineral microparticules could have adsorbed to oil droplets and mitigated adhesion in the process. This may well have stabilised the oil droplets and prevented them from recoalescing in exposed locations.
A research programme conducted by AEA Technology will determine whether these assumptions are founded or not.

 

Oil emulsion in Tenby Bay
Oil emulsion in Tenby Bay
Oil emulsion on the beach in Swanvilake Bay
Oil emulsion on the beach in Swanvilake Bay

Crude

Name: Forties 
Density in kg/l (15 °C): 0.84
API Density: 36.9
Pour point (° C): (- 12 ; + 3)
Viscosity (cSt): 9.6 at 10°C, 7 at 20°C

Composition (%vol)

C1-C4: 2.74 
C5-95° (petrol): 9.23
95°C- 49°C (naphtha): 20.02 
149-232°C (kerosene): 14.50 
232-342°C (gas oil): 20.92 
Sulphides (% weight): 0.32 
Asphaltenes (% weight): 0.20 
Paraffins (% weight): 7 
V/Ni (ppm/ppm): 3/2 
Residues (% vol at 343°C): 40 
- Viscosity (cSt at 50°C): 102 
- Sulphides (% weight): 0.40 
- V/Ni (ppm/ppm): 6/46 
Observations (%vol)

Observations

Thirty to forty per cent of the oil evaporated after 24 hours
Emulsion: viscosity > 10 000 cSt in seawater after 5 days at 5°C

Last update: 17/07/2003