Within the next few years, a couple of major decommissioning projects are set to start in the UK sector of the North Sea at the Brent and Murchison fields — and there are plenty of other projects in the pipeline. John Bradbury outlines the activity.
 |
|
Mattresses on back deck of Bibby Sapphire. |
Finally, decommissioning activity is ramping up in the UK North Sea. During the next two years, some 25 decommissioning projects will be coming forward for consultation and approval, including those already currently in consultation, according to Audrey Banner, head of offshore decommissioning at the UK’s Department of Energy and Climate Change (DECC).
This is compared to about 5-8 per year in previous years and the 54 expected during the next five-year period. Some are multi-installation facilities, with several platforms at one facility, as well as smaller subsea tiebacks, well heads, pipelines and other equipment.
Spending increasing
Decommissioning spending has been increasing on the UK Continental Shelf (UKCS). In its 2015 Activity Survey, Oil and Gas UK said just over £1 billion (US$1.5 billion) was spent on decommissioning activity in 2014, the highest annual spend on record, “accounting for nearly 4% of total UKCS expenditure in 2014. This is set to rise significantly over the next five years and could surpass £2 billion ($3 million) in 2018,” according to the report. What’s more, the lowered oil price could also precipitate more facilities toward decommissioning.
Previous estimates of the size of the UKCS decommissioning market make for sobering reading. There are, according to DECC, 470 installations to be decommissioned. Of those, 10% are floating installations, 30% are subsea, 50% are small steel jackets and another 10% are large concrete or steel installations, which are cases for derogation from the OSPAR Commission (named after the Oslo and Paris Conventions held in Paris) requirements to remove them.
The same DECC data, presented at a Subsea UK event last year, pointed to 44 proposed decommissioning programs being assessed, with an estimated £7-8 billion ($11-12.7 billion) of decommissioning activity expected in the following 3-5 years, and another 63 programs on the horizon. Some of it is big. Banner said there are eight large concrete substructures and 32 steel jackets greater than 10,000-tonne, as well as 244 other steel jackets, 311 subsea production systems, 30 floating production systems, and 3300 pipelines with a total length of 25,000km (15,625mi), 5000 wells and about 200 cuttings piles that could be decommissioned.
 |
|
Bibby Sapphire in port during mobilization. Image from Bibby Offshore. |
Work to date
Decommissioning activity has been building up slowly over the past three years with a string of program approvals.
In 2013, three decommissioning programs were approved by DECC, including the BP-operated Miller field; the BP-operated Schiehallion phase one development, and for recovery of subsea hardware at the Hess-operated Ivanhoe and Rob Roy fields.
Last year, DECC counted 21 proposed programs. Two field decommissioning programs were approved, one for Murchison, and one for the Renee and Rubie fields.
The Canadian Natural Resources-operated Murchison field, found 240km northeast of Shetland, started production in 1980 and ceased in 2014. The 24,584-tonne topsides and eight-legged steel platform down to the top of the jacket footings at 44m (144ft) above the seabed are to be removed. A Murchison export pipeline is to be left in place, while infield flowlines and umbilicals are being removed from recycling or reuse.
At the central North Sea, Renee and Rubie fields, which started production in 1999, and are operated by Endeavour Energy, following a site survey last October, contractor Bibby Offshore, using two vessels, Bibby Sapphire and Olympic Ares, was due to complete the recovery of subsea equipment in June. Well abandonment at the fields is due in 2016.
This year, DECC has approved Centrica Energy’s Rose and Stamford field decommissioning program, comprising a single production well each in the southern North Sea (SNS). Centrica proposes to remove wellhead protection structures and leave export pipelines buried in place.
In consultation
 |
|
Since being removed in 2011, Perenco’s Welland platform topsides has been refurbished and re-installed offshore Cameroon as the Sananga 1 platform. Photo from Perenco. |
An increasing number of projects are also in consultation or the planning phase. In total, 18 decommissioning projects are listed on DECC’s radar, as listed on the Project PathFinder database.
Currently, eight of those, covering nine fields, are under consultation with DECC. These are Leadon, Brent Delta, Thames Area complex, Thames Gawain, Thames Arthur, Thames Orwell, Thames Horne and Wren, and Thames Wissey.
Recently, Fairfield Energy indicated it will cease production at its Dunlin Alpha assets in the UK Northern North Sea in June this year.
Dunlin Alpha is another giant, with a 320,000-tonne gravity base structure (GBS), including 81 previously decommissioned storage cells and 25,000 tonnes of topsides. Fairfield Energy recommends removing the topsides modules and leaving the GBS in place, with a 31m (100ft) tower installed with navigation warning lights.
Proposed plans
Perenco has responsibility for decommissioning a Thames area complex, also in the SNS, where the proposal is to remove wellhead platforms, jackets and subsea installations, and pipelines are to be buried in place. It also proposes to remove wellhead protection frames and bury pipelines in place at the Gawain and Arthur fields within the Thames area.
Tullow Oil is responsible for four fields within the Thames area. At Horne and Wren, it proposes to remove topsides, jackets and subsea installations. Pipelines are to be left in place. Tullow also proposes to remove wellhead protection frames, and leave pipelines buried at the Orwell and Wissey fields, also within the Thames area.
Eni has to deal with four SNS gas field assets, Big and Little Dotty, and Dawn, for which cessation of production (CoP) is under discussion with DECC. Hewett is being considered for reuse as a gas storage site.
Shell’s plan for total removal of the Brent Delta topsides is also still with DECC. Delta ceased production in December 2011, and Alpha and Bravo in November 2014. Brent Charlie is still producing and is expected to continue beyond 2018. Well plugging and abandonment work at Alpha and Bravo is underway, after Delta well plugging completed in 2014.
Delta is supported by a 17,000-tonne steel jacket, most of which is to be removed. But the other three installations are supported by GBSs, which are expected to be left in place due to the technical difficulty and risk removing them.
CNOOC, which acquired Nexen and its assets in the North Sea in 2013, is looking to decommission the Ettrick and Blackbird fields, for which CoP is expected between 2016-2018, with project execution thereafter. Ettrick and Blackbird are tied back to the Aoka Mizu FPSO in the Central North Sea.
At the Maersk Oil-operated Leadon field, the FPSO, Global Producer III, left the field in July 2006 and was redeployed on Maersk’s UK Dumbarton field.
Maersk proposes to leave a pipeline bundle in place at Leadon, but will remove towheads and midline structures spools, jumpers and a gas import line.
Marathon Oil is starting to address decommissioning at its three-platform Brae complex in the UK northern North Sea, while Premier has liability for the Glamis field in block 16/21a, where production started in 1989 and is tied back the Balmoral field and for which CoP is also under discussion.
Subscribe
