In February 2017 Shell lodged plans to the Department for Business, Energy and Industrial Strategy (DBEIS) to undertake the decommissioning of offshore petroleum installations in the Brent Field, located in the North Sea, north east of the Shetland Islands. The Brent field is an iconic field, having commenced production in 1976, producing a sweet light crude oil that has been used as a benchmark crude, serving as a reference price against which other crudes are measured. However, given the decline of production from the Brent field, the Brent benchmark crude now comprises a mix of crudes from the Brent, Forties, Oseberg and Ekofisk Fields in the North Sea.
The Brent field is a giant field with installations to match: the topside of the 4 platforms being removed range between 16,000 and 31,000 tonnes. Three of the Brent installations (Bravo, Charlie and Delta) comprise concrete legs, known as ‘Gravity Based Structures’ (GBSs) (also known as Condeep Structures), which vary between 290,000 and 340,000 tonnes. In its detailed decommissioning plan that has been lodged with DBEIS, Shell recommends that the three GBSs remain in place, since they cannot be refloated or dismantled in one piece. This is seen as the best option based on technical, safety and cost grounds. Shell proposes to remove the top of the installations and seal the GBSs with concrete caps, and fit navigation aids. The decision to leave the GBSs in place has not been taken lightly. In its Decommissioning Plan, Shell outlines the reasons for leaving these structures in place. In particular, Shell stresses that these supports are made from very thick concrete with steel bars and solid ballast, and were anchored down during installation by flooding the legs with water. The GBSs were not intended to be removed once they had been placed on the seabed, and at the time these platforms were designed and installed, there was no requirement to remove such structures. These GBSs have been extensively used in the North Sea (both in the UK and Norwegian Sectors) as they provide the best stability in the rough North Sea, and have the added advantage of enabling oil to be stored in them if required.
It is Shell’s recommendation to leave the Brent GBSs in place that have united environmental groups to oppose the plan. This is not the first time that Shell, or the decommissioning of Brent Field installations, has come to the international attention. In 1995, after three years of evaluation of options, Shell was authorised by the UK Government and the OSPAR Convention (the Convention for the Protection of the Marine Environment of the North-East Atlantic) to dispose of the Brent Spar, an oil storage and tanker-loading buoy from the Brent Field, on the North Feni ridge, in over 7,000 feet of water. What followed was international outrage, with Greenpeace playing a lead role. At the heart of the opposition was the contention by Greenpeace that over 5,500 tons of oil remained in the Brent Spar, a figure countered by Shell who said only 50-100 tonnes remained. After a series of protests and boycotts in Germany and Northern Europe, Shell withdrew their plan to scuttle the Brent Spar in deepwater, with the Spar instead dismantled by Det Norsk Veritas in a Norwegian fjord. Soon after the withdrawal of the plan to scuttle the Brent Spar, the UK Energy Minister called the Greenpeace campaign ‘completely misleading’, leading to a public apology by Greenpeace for its mistake in the estimation of the amount of oil remaining in the Spar.
In the latest controversy to affect the Brent Field, environmental groups claim that the proposed decommissioning plan may be in breach of international law. The two main international law instruments related to the decommissioning and disposal of disused installations is the United Nations Convention of the Law of the Sea (UNCLOS) and the OSPAR Convention. Under UNCLOS, there are a number of general duties to protect the marine environment, particularly Articles 191 and 192. The primary law relating to the OSPAR convention is the decision of the OSPAR Commission after the Brent Spar incident, known as OSPAR Decision 98/3 on the Disposal of Disused Offshore Installations. Under this decision, the dumping or leaving in place (wholly or partly) of disused offshore petroleum installations is prohibited within the OSPAR maritime area (which covers the Brent Field). There are, however, exceptions to this prohibition, including:
- steel installations weighing more than ten thousand tonnes in air;
- gravity based concrete installations;
- floating concrete installations;
- any concrete anchor-base which results, or is likely to result, in interference with other legitimate uses of the sea.
Given the weight and nature of the structures, it is well within the OSPAR convention exceptions to leave the structures in place, in line with the ability to remove the GBSs, and whether it is safe to do so.
Indeed, it is important to realize that there are instances where the removal of a structure may well pose a greater threat than leaving it in place. Such a threat can be to the environment itself (such as the debate surrounding the rigs to reef program) and safety to those undertaking the removal of the installation. Indeed, in the 2000s the MCP-01 concrete platform, located in the North Sea, was decommissioned. The MCP-01 was also a GBS, containing 386,000 tonnes of ballast. After a consideration of all possibilities for removal, the decision was made to leave the subsea GBS structure in place, with as much of the equipment and materials as practicable removed from the concrete substructure and reused/recycled. The primary reason for this decision was the risk to workers, particularly those involved in demolition, marine operations and offshore diving operations.
Whatever decision the UK government makes regarding the decommissioning plan for the Brent Field, it is essential that considerations beyond environmental groups’ interest be considered. Such a decision on whether to leave the GBSs in place need to also consider the safety of those undertaking the removal and recycling, and whether more environmental harm will be caused by removing a 300,000 tonne structure that has been in place for over 40 years. Whatever happens, the ensuing debate regarding this issue is sure to be interesting.
Blog by Professor Tina Hunter