Decommissioning and abandonment

Decommissioning and abandonment

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Some aspects of pipeline removal may involve danger to the diving team charged with removal of equipment. For example, the lifting of mattresses may involve the use of hooks/ lifting lugs well outside their certification date. With the sandwaves in the southern North Sea and elsewhere, and the soft mud of the GoM, West Africa and Brazil, unburial equipment may no longer be able to reach the depth they are now covered to. The weight of soil and destruction of the seabed during removal operations effectively prevents removal. Finally, the operating company’s own reputation should be included. The press and other media can quickly distort the real picture – a case of ‘give a dog a bad name’ – particularly when dealing with the oil industry. EUROPEAN AND US APPROACHES ‘EVERYTHING TO BE REMOVED’ ƒ OSPAR July 1999 ƒ Signed at ministerial meeting in Sintra, Portugal ƒ Presumption of total removal ƒ Concentrates on offshore rigs and wellheads ƒ Larger structures may be ‘derogated’ ƒ Pipelines likely to be assessed case-by-case ƒ Flowlines probably removed along with wellheads ƒ Trunk lines left in place – except at shoreline ƒ BOEM/BSEE removal studies ƒ Same approach but slightly different interpretation ƒ All large lines ‘deemed to be an obstruction’ to be removed ƒ Some deepwater infield flowlines may be left (buried in mud) The OSPAR meeting decreed that the approach to be followed must minimise damage to the environment. The basis of the treaty is that everything will be removed apart from those items that are ‘derogated’ or exempted, after an impact and risk assessment study. Smaller platform structures must be removed. Larger structures may be partly demolished and removed, apart from sections that would be difficult or dangerous to take away. Pipelines may also be dealt with on a case-by-case basis. The UK DTI guidance means that it is expected that wellheads and associated flowlines will be removed, whilst the large diameter trunk lines to shore will be capped and left in a safe condition, apart from at the shoreline, where they will be removed. In the USA, the same basic assumption is used, in that everything should be removed. However, it is expected that BOEM/BSEE (Bureau of Ocean Energy Management / Bureau of Safety & Environment Enforcement) will allow small flowlines to be left buried in the mud, whereas the larger diameter trunk lines must all eventually be removed. The decision of the BOEM/BSEE Regional Supervisor will determine whether a line is an obstruction and thus require its removal, under code 30 CFR 250.1754. Other applicable regulations are 30 CFR 250.1750 to 1754 and 30 CFR 250.1006. The BOEM / BSEE grants a 61 m (200 ft) ROW corridor for trunk lines and their license requires removal within 1 year of cessation of use: nevertheless, there is a waiver granted in 95% of cases. Only pipelines that are an obstruction have been removed. EUROPEANANDUSAPPROACHES‘EVERYTHINGTOBEREMOVED’