OMV Tornado SERPENT final report

Abstract

This report covers the work of the SERPENT Project at the deep water Tornado well in the Faroe-Shetland
Channel (FSC). The surveys will investigate how sediment conditions and animal communities around the
drilling location change from the baseline to a disturbed situation.
The baseline sediment consists of a mix of sand, gravel and occasionally larger pebbles, cobbles and
boulders characteristic of past ice rafting. Attached to the pebbles and boulders were a variety animal life. A
total of 34 animal species were observed living on or associated with the seabed at Tornado, with
megafaunal representatives (i.e. those animals greater than 10 mm) from at least 8 animal groups (phyla).
The species complement was similar to that found from 1000 to 1200m depth in this area of the FSC.
Crinoids (probably all Poliometra prolixa) were considerably more common at this site than elsewhere in
the FSC.
After drilling and cementing the 17.5” section drill spoil (cuttings, mud and cement) was found to extend to
150 m from the centre of drilling (down current; SW direction). The approximate total area of seabed
disturbed was 17400 m2. Drill spoil vertical height was at least 3m close to the drill site.
The number and diversity of animals found at Tornado decreased dramatically after drilling, particularly
close to the drill site, where animals were covered with sediment. After drilling the 17.5” section the
number and diversity of animals increased with increasing distance from drilling. The animals present in
disturbed zones were mostly mobile forms or sessile organisms on rocks elevated above the drill spoil.
Owing to the limited survey extent of 100m, the most disturbed transect directions (e.g. SW) had extremely
limited animal numbers throughout their entire length, indicating high disturbance conditions.

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