Seepage from the seabed can have many causes. It can occur in connection with human activity or be caused by natural processes. There has been a greater focus on seepage from the seabed recently, where seepage of methane gas from or around wells drilled in connection with petroleum activity has been mentioned and discussed.

Multiple authorities, different roles

In technical terms, seepage from the seabed covers a great many disciplines and specialist agencies: the Petroleum Safety Authority (PSA), the Norwegian Environment Agency (NEA) and the Norwegian Petroleum Directorate (NPD) are all involved in various issues.

For the PSA, these issues relate to factors such as safety and well integrity; important seepage topics for the NEA could include the impact on ecosystems, and could factor into the national emissions inventory; and for the NPD, seepage entails greater understanding of the subsurface, and contributes to better management of the petroleum and seabed mineral resources on the NCS.

Knowledge and oversight

Causes, risks and effects associated with seepage from the seabed were some of the topics raised at a technical workshop on 17 February, which included the respective responsible ministries. The workshop was a joint initiative from the PSA, NEA and NPD.

The objective of the workshop was to gather knowledge and an overview of what has been done in the area. Based on the available information, it will be easier to assess knowledge gaps and gain a better understanding of how they can and should be dealt with.

Geology

Rune Mattingsdal from the NPD talked about how mapping and analyses of natural seepage can be used to evaluate geological development and the petroleum resources on the Shelf. Through a cooperative effort including e.g. the CAGE research centre in Tromsø (see below) and analyses, particularly of water column data, several thousand natural seepages have been detected, particularly in the Barents Sea. Thanks to aerial and satellite data, it has also become clear that natural leakages of oil from parts of the Barents Sea do indeed occur.

Climate

CAGE – the Centre for Arctic Gas Hydrate Environment and Climate was presented by the head of the centre, Professor Karin Andreassen. The aim of the research centre is to enhance knowledge about what could happen with the huge volumes of methane gas found in the Artic, particularly in the form of gas hydrates, when temperatures rise and cause the frozen parts of our earth to thaw.

Leakage points

Terje Thorsnes from the Geological Survey of Norway (NGU) presented the Mareano programme, emphasising activities that increase knowledge about seepage of gas from the seabed. From 2010, water column data has been collected from an area of 170,000 km2, mainly in the Barents Sea and the Norwegian Sea, which is now being reviewed and interpreted. About 1,900 probable and certain leakage points have been identified so far. The plan is to publish a database and map of proven leakage points sometime during 2021.

Natural seepage

At the Centre for Deep Sea Research at the University of Bergen, Professor Rolf Birger Svarstad Pedersen emphasised emissions and processes in the structures along the mid-ocean ridge. Driven by deeper magma, huge volumes of water circulate through the crust and lead to seepage of various types of gases, as well as precipitation of minerals along these geological structures in very deep waters.

The way forward

The PSA, NEA and NPD are planning a joint initiative to follow up all the diverse and complex issues raised in the meeting on 17 February.

This will be done in various ways, including dialogue with the petroleum industry, as well as through further collection of knowledge from various research and professional communities.