Asterix SERPENT visit report

• Main Authors: Gates, A.R., Jones, D.O.B.
• Format: Book
• Language: English
• Published: National Oceanography Centre 2010
• Subjects: Norwegian Sea
• Online Access: https://eprints.soton.ac.uk/160923/; https://eprints.soton.ac.uk/160923/1/73_Asterix.pdf

This report presents the results from the SERPENT project collaborative research with StatoilHydro at the Asterix deep-water exploration oil well, drilled from the Transocean Leader in the Norwegian Sea. The study was designed to investigate seabed disturbance resulting from the drilling activities at Asterix and the effects of these activities on the benthic environment and megafaunal organisms. The ROV Magnum 018, was used to take eight video transects of at least 100m in length which were used to assess visually the extent of drill cuttings and to determine megafaunal densities. Also a series sediment samples were collected using ROV operated push cores at 50, 80 and 100m from the well to determine heavy metal concentrations, total organic matter and particle size distribution. Comparison of these methods suggested disturbance was variable depending on heading but suggested complete coverage of the seabed up to 60m from the well and partial coverage to 100m. Analysis of the sediment showed elevated Barium concentration in surface sediments at all sample locations, decreasing with distance and with depth sections. At the site closest to the well mean particle size increased in comparison to the background sediment. These physical changes were associated with significant reductions in megafaunal abundance and changes in the megafaunal community structure, with very few animals observed in a 50m radius of the well. Small ophiuroids were extremely abundant at the site reaching up to 20m-2. Similar to the megafauna, their numbers were reduced by the disturbance event and density was significantly reduced within 80m of the well. Details of a short documentary film made by StatoilHydro about the SERPENT collaboration on board the Transocean Leader are also given here.