Slipping into the lead
23/02/2007 The chance of more landslides around the Ormen Lange gas field in the Norwegian Sea has been extensively studied, giving researchers in Norway world-class expertise in this area.
Text: Ina Gundersen
The Storegga slide
An area off mid-Norway about the size of Iceland experienced a massive landslide some 8 100 years ago in water depths from 300 to 2 500 metres.
The displaced soil travelled up to 800 kilometres, creating a tsunami which washed over the Norwegian coast and up into its fjords – where the flood waters were up to 20 metres high.
Due to come on stream in the autumn of 2007, Ormen Lange lies in the centre of the depression created by the Storegga event, and close to its very steep edges.
Ahead of the development of this field, extensive studies were conducted to determine the threat of new land movements.
These established that the conditions which caused the Storegga slide are no longer present. A new ice age would be needed to recreate them.
Ormen Lange lies in the centre of the depression left by the slide and close to its very steep edges. That has prompted very extensive efforts to map the threat of new displacements. Illustration: Norsk Hydro
The Ormen Lange field lies in the depression created by the Storegga clay slide, one of the largest displacements of the seabed in the world.
Development operator Norske Hydro and much of Norway’s geoscience research capacity has been involved in seeking to determine whether this natural disaster could repeat itself.
“These detailed studies have given Norway a unique expertise on the subject of underwater landslides,” observes NPD geologist Fridtjof Riis.
In addition to the Norwegian Geological Survey (NGU) and the Norwegian Geotechnical Institute (NGI), this work has involved the universities of Oslo, Bergen, Trondheim and Tromsø.
The research collaboration with Hydro has made an important contribution to the oil and gas industry and the Norwegian geosciences community, says Haflidi Haflidason.
A professor in the department of geosciences at the University of Bergen, he notes that the scale of the problem meant more disciplines had to be brought in.
“That’s enormously enhanced our expertise, which is in demand from the oil and gas industry both at home and internationally,” he adds.
His department helped to establish why the Storegga area is unstable, where the slide was initiated and how it developed.
Although there is no threat of new seabed displacements around Ormen Lange, he and the NGU want to continue studying the Nyegga area at the northern edge of the slide.
“More mapping and improved geological understanding of this region is needed with an eye to possible future petroleum developments,” he emphasises.
Work on the Storegga event has also helped to propel Norwegian scientists into the international front rank of research on tsunamis - the waves generated by seabed disturbances.
Among them are Carl Harbitz of the International Centre for Geohazards at the NGI in Oslo, whose work in the Ormen Lange project has helped to make tsunamis a key ICG research area.
“Goals included developing the best possible models to understand the processes which can unleash tsunamis, and to predict the size and extent of such waves,” he explains.
The ICG is also involved in a project to study tsunamis in European waters. This project recently received financial support from the European Union.
“Thanks to Ormen Lange, Norwegian researchers have become more visible internationally,” Prof Harbitz adds. “That’s one reason for our inclusion in this type of EU project.”
Tore Kvalstad at the NGI headed studies to determine whether the seabed in the Storegga slide area is stable enough to bear the Ormen Lange installations without risking a new displacement.
He says that the work on and openness around this development has prompted the international oil and gas industry to contact the institute with offers of new jobs.
“We did very extensive field work and collected a lot of samples for testing,” he reports. “That permitted technical calculations of the slide risk on Ormen Lange and the scope of the original event.”
Geotechnical data for submarine slides elsewhere in the world have otherwise proved very limited.
“Since we finished on Storegga, we’ve been contacted to participate in similar incidents elsewhere, Mr Kvalstad reports. “These include big deltas off Egypt and India.”
Some NOK 1.3 billion has been spent on investigating the continental shelf margin – where the descent to the ocean floor begins – and the threat of a new Storegga disaster.
“Research cooperation around this area has been unique in a world context,” says Petter Bryn, project manager for clarifying the landslide threat at development operator Norsk Hydro.
Pursued in 1996-2003 under Hydro’s leadership, the Storegga project involved collaboration between Norwegian scientists and researchers from the European Union.
Institutions involved include the universities of Oslo, Bergen and Tromsø, the Norwegian Geological Survey, the Norwegian Geotechnical Institute, Norsar and Sintef.
Cooperation established in 1996 with an existing EU project studying sedimentary processes in the continent’s deepwater margins led later to partnership with several EU programmes.
“Full exchange of data was established between our project and the EU schemes,” says Mr Bryn. “That meant we were working with most of the experts on issues relating to landslip hazards.”
He emphasises that the most important reason for the success of the Ormen Lange investigation – in the form of a conclusion that everyone accepted – was the creation of an open cross-disciplinary collaboration between disciplines and institutions.