|Location:||Midnattsol, Norwegian Sea, Norway|
|Water Temperature:||No data|
23 - 29 Aug 2007 (Post-drilling visit)
|Gas & Oil Company||Statoil|
|SERPENT Representative:||Dr Andrew gates|
This quick-look report summarises the recent SERPENT visit to the Transocean Leader semi-submersible deep-water drilling rig at Midnattsol. The visit was carried out in collaboration with Statoil in August 2007. Midnattsol is located in Block 16-2 of the Norwegian Sea, 130 km west of Kristiansund (Figure 1) and is one of three wells included in the SERPENT collaboration with Statoil for 2007.
The aim of the mission was to assess the effects of disturbance on the deep sea communities in relation to drilling operations by carrying out a number of surveys during two visits to the well; one before any drilling operations had begun and a second towards the end of the drilling operations. The first visit was used to take pre-drilling video transects and push core samples as well as to set up sediment marker buoys to assess the accumulation of drill spoil, procedures which were repeated during the second visit. The pre-drilling visit also offered a good opportunity for SERPENT researchers to gain detailed understanding of the study area which is beneficial in the planning of the subsequent visits to the site.
During the pre-drilling visit the Oceaneering Magnum 018 work class ROV was used to collect video transects centred on the proposed location of the BOP prior to any disturbance. In addition three similar transects were taken shortly after drilling had commenced on a pilot well 50 m to the NW of the main well location.
Sediment samples were collected using ROV push corers in order to establish the chemical characteristics and the meiofaunal composition of the seabed at the well location before drilling began. The new design SERPENT push corers, first trialled in deep water on this visit, proved successful and the sediment was suitable for further push coring on the follow-up visit.
During the follow-up visit these procedures were repeated in order to assess the horizontal extent of drilling disturbance and its effects on the biological communities surrounding the well. Measurements were also taken from previously deployed sediment marker buoys to determine the vertical accumulation of drill spoil during the operations.
The opportunity was also taken to further the experimental work carried out by SERPENT. Bioturbation experiments were carried out to investigate the rate of reworking of the sediment by the infauna, an important factor in the consideration of the recovery of areas of seabed after the impacts of drilling disturbance.
Basket stars, probably Gorgonocephalus caputmedusae were common at the Midnattsol well location during the second visit. Here, there is an example of a basket star on a seabed feature with its arms extended for filter feeding. The close-up on the right shows the intricate branching of its arms as an adaptation for this mode of life. A tubularian hydroid and an alcyonacean soft coral are also present in the picture on the left.
A cirrate octopus (left) was observed in the water column on transit between a sampling station and the ROV cage. Pycnogonids (right) were common on the seabed, this is an example of Colossendeis proboscidea.
Fish were rarely seen at Midnattsol. Those that were observed during the post-drilling visit included, left, scorpion fish (Cottunculus sp.) and an unidentified species of ray.
For further information please contact:
Dr Andrew Gates, SERPENT Project, National Oceanography Centre, Southampton, UK.
or Dr Daniel Jones, SERPENT Project, National Oceanography Centre, Southampton, UK