Cashel

Mission 1

Images | Videos

Location: Cashel, Northeast Atlantic, Republic of Ireland
Position: 54° 42’ 23.58” N 10° 26’ 20.37” W
Depth: 174 m
Water Temperature: 10ºC
Dates: 18 – 22 May 2008
Industry Partners  
Gas & Oil Company Statoil
ROV Operator: Oceaneering
Rig operator: Diamond Offshore
SERPENT Representative: Dr. Andrew Gates
   

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Mission Plan

This mission report summarises the recent SERPENT visit to the Ocean Vanguard semi-submersible drilling rig at the Cashel field.

This was the first SERPENT visit to a rig off the coast of the Republic of Ireland and was the first in a series of offshore visits, including two more to Cashel, planned for 2008 as part of the SERPENT collaboration with StatoilHydro.

Primarily the aim of the visit was to use the ROV to conduct an initial survey of the seabed in the area to get a good understanding of the fauna so that we can return to the rig later in the drilling programme and carry out some experimental work in order to gain a better understanding of the effects of drilling operations on the marine life and their potential for recovery from the disturbance.

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Survey

The initial survey showed some disturbance to the sea bed caused by the drilling of the 36 section and this will be monitored with additional surveys on the subsequent SERPENT visits. Of most interest was the type of benthic environments in the area. There were very rocky areas and patches of finer sediment. These different habitats should provide interesting contrasts for studying the effects of the drilling on organisms adapted to hard and soft substrata. Examples of the different environments can be seen below.

Hard and soft seabeds

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Eco Highlights

Perhaps the most important outcome from this initial visit to Cashel is the documentation of the different species in the area. This was done using the video camera system on the ROV. This enables us to know more precisely which animals have been seen in the video surveys and gives us an understanding of the ecology of the area in order to plan experimental work for subsequent visits. Video and photographs of the animals seen at Cashel can be viewed in the SERPENT database. Examples of the organisms seen at Cashel are shown below.

Seastar image

Echinoderms, particularly asteroids, were common at Cashel. This one, probably Luidia sp. was one of the larger examples.

Asteroids, Sunstar left and Porania pulvillus right

Other Asteroids at Cashel included the spectacular sunstar (left) and Porania pulvillus (right) seen here with its body wrapped around a hydroid it is feeding on.

Octopus

This octopus, hiding behind a rock, was the only example seen at Cashel.

Hermit crabs

Hermit crabs were abundant on the sea bed at Cashel. They were regularly seen scuttling across the sea floor during the video surveys. Here many of them were observed in one area.

Dogfish

Dogfish were common at Cashel. These small sharks were inquisitive, often coming up to investigate the ROV, perhaps to find morsels of food stirred up from the sea bed by the thrusters on the vehicle.

 

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Cashel location map Dr Andrew Gates

About Andy
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T: +44 (0)2380 596363
E: arg3@noc.soton.ac.uk