2001 Strategic Environmental Assessment SEA2 Technical report - Pockmarks in the UK sector of the North Sea
This report is a contribution to Strategic Environmental Assessment SEA2 conducted by the Department of Trade and Industry (now Department of Energy and Climate Change) and it reviews the distribution and character of pockmarks - shallow seabed depressions - which are common in the area of the North Sea to the north-east of Scotland known as the Fladen Ground. Pockmarks are believed to be produced by the escape of fluids (gas or water, but generally gas in the North Sea) from the seafloor and are found in areas where the seabed sediments are soft, silty clays. Processes of pockmark formation, their geometry, age and distribution, and the sources of gas in the underlying geological strata are discussed. While the great majority of pockmarks are inactive at the present time, a few are observed to be actively seeping gas.
In order to provide a stronger basis upon which the significance of pockmarks within mature oil and gas provinces of the North Sea might be assessed, the Department of Trade and Industry commissioned the acquisition of new data directed towards increasing the scientific understanding of sandbanks and pockmarks as part of the SEA2 process. The survey vessel Kommandor Jack was chartered in April 2001 and, among other operations, conducted high-resolution geophysical surveys of pockmarks in the Fladen Ground. Preliminary results from that operation are included in this report.
dataset
Strategic Environmental Assessment (SEA) data portal
- The Strategic Environmental Assessment (SEA) data portal provides free access to available data and reports which have been produced through the UK Department of Energy and Climate Change SEA process. The site is run and managed by BGS on behalf of the Department of Energy and Climate Change (DECC). Many files can be downloaded directly from this website. Those that are too large to download can be ordered via the website for postal delivery from BGS.
Murchison House, West Mains Road,
Edinburgh,
EH9 3LA,
UK
tel: +44 (0)131 667 1000
email:
offshoredata@bgs.ac.uk
Role: custodian
Department for Energy and Climate Change (DECC)
Admiralty Way,
London,
SW1A 2HD,
UK
tel: +44 0300 060 4000
email:
enquiries@decc.gsi.gov.uk
Role: originator
Data Quality
In April 2001 the survey vessel Kommandor Jack among other operations, conducted high-resolution geophysical surveys of pockmarks in the Fladen Ground as part of the UK Department of Energy and Climate Change's Offshore Energy Strategic Environmental Assessment programme. Geophysical surveying was undertaken using the following equipment: Swath Bathymetry: Simrad EM1002; Side scan sonar: Geoacoustics 159; Sub-bottom profiling: Datasonics Chirp profiler; Positioning: DGPS. This report was prepared by Dr Alan Judd (University of Sunderland) in 2001. Data from offshore site survey reports (made available by the British Geological Survey with permission of the relevant oil companies), as well as published and publicly available material were also used to compile the report.