The Ormen Lange marine archaeology project

Abstract

The Ormen Lange field is located in the Norwegian Sea, 100 kilometres north-west of the coast of Mid-Norway. It is Norway's largest gas field, and was proven through drilling by Norsk Hydro in 1997. The development of the Ormen Lange field includes installation of a subsea production system, which will be piped directly to an onshore process and export plant. The pipelines pass through an area that is on the Norwegian Directorate for Cultural Heritage's list of areas with special priority for marine archaeology and protection of underwater heritage. The area was visited by Norwegian and foreign vessels since the Middle Ages in connection with rich herring fisheries, timber trade, general trade, and naval operations. Norsk Hydro presented existing survey data from their proposed pipeline routes. Although the multibeam and sidescan surveys had detected 8 modem shipwrecks in the area, it was decided that the existing survey data were inadequate to detect, with reasonable certainty, the presence of archaeological material in the proposed pipeline corridors NTNU therefore carried out a marine archaeological survey in the planned pipeline corridors in August and October 2003 to fulfil the requirements in the Norwegian Law on Protection of Cultural Heritage. The team utilised a 60-feet catamaran equipped with a Kongsberg Simrad DP system, and a Sperre ROV equipped with Kongsberg Simrad sonar and camera equipment to locate shipwrecks in the pipeline corridors. The ROV was flown along the centreline of the pipeline routes. Sonar images were interpreted on the fly and used to locate potential targets. When an interesting target was located, the ROV was flown to it and the target was inspected using the ROV's video cameras, while the survey ship was holding position. During the surveys in August and September 4 modem and 2 historical shipwrecks were discovered in or close to the planned pipeline routes. The most important discovery was a historical shipwreck situated close to the planned pipeline routes. It was detected by the sidescan sonar system used as the primary survey instrument, in concert with the ROV cameras used for visual inspection of the seafloor and seafloor anomalies. Upon closer inspection it was determined that the site was a historically significant wreck, in a state of good preservation. The site contains thousands of artefacts, some exposed on the seafloor surface while others are buried under several centimetres of sandy-silt that is being transported across the site by tidal currents.