| Location: | Schiehallion, Transocean Leader |
| Position: | Faroe-Shetland Channel |
| Depth: | 508m |
| Water Temperature: | No data |
| Dates: | 2003 |
| Industry Partners | |
| Gas & Oil Company | BP |
| ROV Operator: | Subsea7 |
| Rig operator: | Transocean |
| SERPENT Representatives: | Dr Ben Wigham |
Mission Plan
Using the Subsea7 Pioneer HD22 ROV, based on the TOL, a scientific work programme was undertaken which involved video mapping of the seabed, sampling for sediments and animals, in situ experiments and trials of ROV science tools.
This project was designed to
- Gain accurate visual information of the seabed habitat around and active drilling rig
- Test the feasibility of using industrial ROVs for completing specific science tasks and the advantages and disadvantages of using existing infrastructure for potential environmental impact assessments and downstream monitoring by the producer client (in this case BP).
During 6 days of intensive ROV use 19 individual video survey lines were completed, experiments were set-up and completed, samples of sediment and the characteristic animals of the area were collected, and new ROV tools and protocols were tested.
Experiments
During the visit to the Transocean Leader drilling rig the ROV was used to deploy simple seabed experimental packages for measuring bioturbation in the sediments. The burrowing and feeding activities of animals living in the sediment will turn over and mix particles, bringing oxygen down to deeper layers of the sediment and also bringing anoxic mud up tp the surface.
In collaboration with the Subsea7 ROV crew and Transocean engineers we designed and manufactured several experimental corrals for use on the seabed. These steel-framed cages are designed to restrict access to the experimental area, reducing the impact of large animals on the disturbance of the sediment.
Luminophore tracers (fluorescent dyed sand) were deposited on the seabed within the corrals. The steel walls of the corral frame also prevented the strong currents from removing the lumiophores from the experimental area. The corrals were deployed in two locations to examine differences in the rates of bioturbation in areas of drill spoil and surrounding untouched seabed. Each experiment was left on the seabed for 48hrs.
The images above show the successful deployment of the corrals and the luminophores on the seabed in 450m water depth, West of Shetland. Analysis of cores taken at the end of the experiment revealed a stratified sediment complex with drill spoil overlaying approximately 5cm of sandy gravel and then mud. The lumiophore particles had been visibly mixed down into the sediment and the core was sliced at 1cm intervals to allow the number of tracers per depth horizon to be counted.
Video of luminophore tracers being deployed in a experimental sediment corral. For further information on ROV experiments contact Dr Daniel Jones .
