Decommissioning and the environment – background and key developments

Decommissioning is the process of removing offshore platforms/installations once they have reached the end of their useful life. Offshore structures are only temporary, and legislation governs their removal and disposal. One of the best known incidences of decommissioning is the case of the Brent Spar where the disposal route, despite being the Best Environmental Option, came under intense public and media scrutiny resulting in the operator of the structure having to seek alternative disposal methods.

The environmental case for abandonment of structures is therefore a clearly emotive issue, however legislation carefully governs what ‘can and cannot’ be done. The principal legislation for this is OSPAR Decision 98/3 on Disposal of Disused Offshore Installations. Under OSPAR legislation, only installations that fulfil certain in-depth criteria are eligible for derogation (that is, leaving the structure, or part of, in place on the seabed) and the remainder of installations must be removed from the seabed.

For further information please visit
http://www.ospar.org

The large steel structure North West Hutton had its decommissioning approval programme approved by the Secretary of State for Trade and Industry in 2006. Offshore removal work is expected to start in 2008. The topsides and jacket will be removed by heavy lift vessel - it is estimated that 97% of the material recovered will be recycled. According to the OSPAR 98/3 derogations ruling the steel jacket footings will be left in place - as it remains unviable to remove these sections to shore. For further information on North West Hutton please visit
http://www.bp.com/genericarticle.do?categoryId=6910&contentId=7030074

Total’s Frigg MCP-01 concrete platform decommissioning programme has also received approval from the Secretary of State. For further information on North West Hutton please visit
http://www.uk.total.com/activities/st_fergus_terminal_mcp.asp

Two further aspects of oil and gas production that must be taken into account at the time of decommissioning include NORM (Naturally Occurring Radioactive Material) Scale and drill cuttings. Installations may require the removal of significant amounts of NORM Scale which will require disposal; however there are no existing estimates of the amount of this material that will arise from decommissioning.

For more information on NORM Scale please visit
http://www.oilandgasuk.co.uk/issues/environment/norm.cfm

For further information on drill cuttings piles, please see the Oil & Gas UK Environment website
http://www.oilandgas.org.uk/issues/environment/index.cfm

Decommissioning and the environment – Key Statistics and Commentary

At the conclusion of exploration drilling, if nothing has been found, the well is decommissioned (using agreed Oil & Gas UK Guidelines) to a clean seabed. The site is then both inspected by cameras and, under an arrangement between Oil & Gas UK and the fishing federations, SFF (Scottish Fishermen’s Federation) and NFFO (National Federation of Fishermen’s Organisations), over-trawled by a fishing vessel. If the exploration or appraisal well finds hydrocarbons, then sometimes the option is taken of suspending the well for future use in a subsequent development.

UKCS Number of Open-water Suspended Wells 1998-2007

The Oil & Gas UK guidelines for the suspension and abandonment of wells can be found on the Oil & Gas UK website
http://www.oilandgasuk.co.uk/ukooa/newpublications