David Knott
Senior Editor
Esso Norge proposed to topple its idle Odin platform for use as a fish reef in the North Sea. However, the Oslo government insisted on total removal, although it has not officially vetoed offshore disposal as an option for other fields. Saipem's S7000 heavy lift vessel this autumn will transport the platform in four loads to a site near Aker's Stord, Norway, yard for recycling and scrapping£.
Producers have begun work on a number of platform abandonment projects off Norway and U.K while still recovering from the shock of last year's dramatic disruption of a plan to abandon the idle Brent spar loading buoy.
Although Brent field operator Shell U.K. Exploration & Production had persuaded U.K. government that deepsea dumping was an acceptable disposal method on environmental grounds, environmental activists were not convinced.
So pressure group Greenpeace took control of the spar in a commando-style raid and created a storm of antidumping protest that grew into an unprecedented environmental battle (OGJ, Nov. 27, 1995, p. 23).
Shell eventually gave up its dumping plan. Even so, the prospect of further protests against North Sea field facility abandonments has hung like a black cloud over the decommissioning issue ever since.
Since the Brent Spar controversy, Norwegian and British operators have slated a number of platform abandonments, but these have been small and unlikely to cause an outcry.
Norwegian and U.K. governments continue to maintain that deepsea disposal of platforms is still a viable option, but the abandonments approved to date show how the governments differ in approach.
No abandonment plans have surfaced off Denmark. A number of complete platform removals have taken place off Netherlands, a shallow water area.
International Maritime Organization (IMO) rules require all platforms in less than 75 m of water to be completely removed, although the limit is expected soon to be relaxed to 55 m.
Under the 55 m clearance limit, about 30% of the North Sea's current 420 or so platforms would be eligible for partial removal or dumping (OGJ, Mar. 20, 1995, p. 31).
With offshore production from the Netherlands in decline, three to five platforms a year are expected to require removal in the near term. All will be completely removed.
Wintershall Noordzee BV removed three small steel platforms from K13 gas field in 1989, and in that same year Unocal removed a platform from Helder oil field. Both fields were off Netherlands.
Abandonment prospects
Plans were submitted to Norway's Ministry of Industry & Energy (MIE) this year to decommission Northeast Frigg and Odin fields. The Northeast Frigg plan has won Oslo's approval, and approval for Odin is expected soon.
Norway's most recent abandonment was by operator Norsk Hydro AS, which developed Mime field as a single well subsea satellite of Cod field, tied into the Ekofisk complex.
Mime production ceased in 1994, and the well was plugged and subsea equipment removed.
Among other operations, Den norske stats oljeselskap AS expects production from Tommeliten gas field, a small subsea satellite of Edda platform, to end in 1997 or 1998. Statoil, which hopes to reuse templates and pipelines installed during development, expects to complete an abandonment proposal this summer.
A Norwegian Petroleum Directorate (NPD) official said major abandonments ahead off Norway are Frigg and Ekofisk fields, both multiplatform complexes.
Ekofisk operator Phillips Norway group expects to shut down most platforms in the field in 1998, after subsidence in the area required installation of new ones under a massive redevelopment plan (OGJ, Aug. 15, 1994, p. 51).
The NPD official said there have been no discussions so far with Phillips and Frigg operator Elf Norge AS over abandonment options. Phillips has said it hopes to leave Ekofisk platforms in place until the field is fully depleted about 2030.
Mackay Consultants of Inverness, Scotland, recently listed U.K. fields it expects to see the end of their lives by 2000. Deveron, Hamish, and Leven field are expected to be shut down this year. Emerald production ended earlier this year. The field has been abandoned.
Mackay expects Don and Northwest Hutton fields to cease production next year, while Heather, Highlander, Maureen, Montrose, and Petronella are expected to stop in 1998, and Blenheim, Carnoustie, Chanter, Kittiwake, and Ness fields will cease production in 1999.
"Most of these are small fields," Mackay said, "but they include three relatively large ones-Northwest Hutton, Heather, and Maureen-which have played important roles in development of the U.K. North Sea.
"Their decommissioning therefore will represent something of a turning point in the history of North Sea oil industry. Their platforms will be the first large ones decommissioned."
Work in progress
U.K. operators will decommission a number of small oil fields and medium size gas fields this year. None of the projects is on such a large scale or as potentially controversial as Brent spar or any of the large platforms.
Lasmo plc has killed and cemented two wells in Staffa field on U.K. Block 3/8b and brought their subsea wellheads to shore. The company is seeking bids for complete removal of a 10 km pipeline that ties the field to Ninian Southern platform.
Staffa, which went on stream in March 1992, had peak production of 11,000 b/d. It produced almost 4 million bbl of oil before its November 1994 shut-in.
Lasmo found unexpectedly high build-up of hydrates in the pipeline, which stopped flowing in 1993 prior to replacement of a 2 km section of pipeline.
When the pipe became completely blocked again in November 1994 despite use of chemical inhibitors, it was decided remaining reserves were too low to justify redevelopment.
A Lasmo official said the company is still debating with U.K. Department of Trade & Industry (DTI) the best option for abandonment of the pipeline.
Midland Scottish Energy Ltd. saw abandonment of U.K. North Sea Emerald field by contractor Nowsco U.K. Ltd., Aberdeen, last February. Emerald was developed using a converted semisubmersible rig tied into nine subsea oil production wells and two water injectors.
Nowsco flooded the export line gas lift and umbilical system, cleaned subsea pipelines, subsea manifolds and production umbilicals, killed the wells, and pumped nitrogen through the topsides. This, said Nowsco, rendered the installations clean and safe prior to cutting the risers and removing the rig for refurbishment.
DTI approved a plan to return the Emerald Producer production semisubmersible to Invergordon for refurbishment so it can be marketed for redeployment. The field's Ailsa Craig storage tanker also will be available.
BHP Petroleum Ltd. has decommissioned the production semisubmersible operations in Crawford and Argyll/Duncan/Innes fields and a platform in Forbes field (OGJ, Mar. 20, 1995, p. 31).
Forbes was a satellite of Esmond field, which is being decommissioned by BHP along with its other satellite, Gordon.
Esmond's central production platform and adjacent wellhead platform and Gordon's satellite production platform are being removed by Heeremac VOF of Leiden, Netherlands.
Production from Esmond and Gordon gas fields ceased in March 1995. Heeremac began heavy lifts to dismantle the platforms in late April using the DB102 crane barge.
Two decks and the accommodation unit of Esmond's topsides were removed first and taken by barge to the Able U.K. Ltd. yard in Middlesbrough to be broken into scrap.
DB102 will remove the remaining deck sections and jackets this month. Esmond's platforms stand in 33 m of water and Gordon stands in 19 m, so complete removal of jackets is required.
Late last month BP Exploration Operating Co. Ltd. let a ٧ million ($13.5 million) contract to Coflexip Stena Offshore Ltd., Aberdeen, for removal of as many as 49 redundant subsea wellheads from the U.K. North Sea.
BP said the CSO Seawell multipurpose ship will remove 30 wellheads in batches from the northern central and southern North Sea during the fourth quarter. The rest will be removed next year as the ship is available.
BP has 69 suspended wellheads throughout the U.K. North Sea, resulting from exploration and appraisal activity.
Depending on their condition, some of the wellheads may be refurbished for further use. The rest will be scrapped. BP said this is the largest single program of its type undertaken in the North Sea.
Viking
Conoco (U.K.) Ltd. last February announced a plan to carry out its first North Sea abandonments, involving removal of four of a group of five platforms in North Viking gas field on U.K. Block 49/12.
Viking A complex, part of a 14 platform development that includes South Viking field on Block 49/17, ceased production in 1991. One platform, Viking AR, has been used as a riser platform since then and will be retained.
The four platforms to be removed were not upgraded under new U.K. offshore safety rules that were implemented in the wake of the Piper Alpha platform blast of 1988.
Conoco said the Viking A complex dates from 1972, and the redundant platforms have been costing significant sums for care and maintenance.
The company has secured DTI approval to remove the platforms this year. Because water depth in the field is only 26 m, they must be completely removed under IMO rules.
The platforms weigh a combined 8,600 metric tons. The Stanislav Yudin heavy lift vessel has been mobilized to the field and is expected to remove the structures in 22 lifts of more than 50 metric tons and 24 lifts of lesser weight.
Components will be taken to Swan Hunter yard on Tyneside. Conoco said 99% of their materials will be recycled, with less than 1% destined for landfill.
Leman
Shell Expro last February won DTI approval for abandonment of a platform in its Leman gas field in the southern North Sea. Leman BK compression platform, one of 15 platforms in the field, stands in only 33m of water and therefore must be completely removed.
The platform is one of three linked, manned platforms in the Leman BT sector of the field, along with the Leman BH accommodation platform and Leman BT trunk line terminal platform.
Shell Expro, operator for Shell U.K. Ltd. and Esso Exploration & Production U.K. Ltd., is converting southern gas basin field platforms to unmanned operations where possible in a bid to reduce operating costs and prolong field lives.
Leman BK's compression function will be handled by the field's other compression platform, Leman AK, which is being refurbished. The BH and BT platforms will be converted for unmanned operation, with BH used by visiting maintenance crews.
Shell-Esso said BK abandonment is expected to be complete this year at a total cost of 㾷 million ($17 million). The company let contract to Heeremac for design work associated with removal of topsides and jacket and their transport ashore.
The BK platform weighs more than 6,000 metric tons, of which 4,600 metric tons is topsides. Major lifts required for removal involve three platform modules, a module support frame, and the jacket.
Sensitive to public opinion after the Brent spar disposal outcry last year, Shell-Esso has published a list of potential contaminants onboard the platform, including about 50 metric tons of heavy metals, almost 1 metric ton of halon and freon compounds, and 3,300 l. of oil.
Shell-Esso said more than 95% of the structure will be recycled. The company expects shortly to let contracts for platform removal and onshore disposal.
Shell Expro let contract to Able for onshore recycling and disposal of its Leman BK compression platform. Shell reckons more than 95% of the structure will be recycled.
Northeast Frigg
Earlier this year, Norway's MIE approved Elf's abandonment plan for Northeast Frigg field.
Northeast Frigg, in Block 25/1, was developed using a six well subsea manifold tied back to Frigg TCP2 platform, with a 150 m articulated control tower to govern well operations.
In January, Elf let a 95 million kroner ($15 million) contract to Kvaerner Installasjon AS and Stolt Comex Seaway AS of Stavanger to remove and abandon the facilities this summer.
Northeast Frigg facilities are to be reused where possible. The wellhead template will be resmelted, flow lines and cables scrapped, and the quarters and work deck moved to a safety training center.
In the nearest move toward acceptance of dumping off Norway to date, the government agreed that the steel articulated column can be laid on a bed of rock to form a breakwater at a new marina near Stavanger.
In the U.K. sector, Elf Norway was given the green light by DTI to remove a flare column in the U.K. portion of Frigg field.
Although this stands in 107 m of water and could theoretically be dumped according to DTI guidelines, removal and towing to shore for dismantling was said to be straightforward.
Odin
After Norway's MIE approved use of the Northeast Frigg tower in building a marina, operators had hopes of being given leeway to dump some structures.
Odin field operator Esso Norge AS submitted a decommissioning plan in March 1995 that proposed removing the platform's topsides and toppling the steel jacket to make an artificial reef.
But the ministry surprised the industry in March this year by insisting that Odin platform, which stopped producing in August 1994, be completely removed.
A U.K. oil industry official said the decision was a setback to Britain's attempts to persuade environmental pressure groups that deepwater disposal is still a viable option after last year's Brent spar battle.
Norway's ministry said Odin platform will be taken to shore for dismantling and recycling, with total decommissioning costs expected to be 245 million kroner ($40 million).
Odin platform is a conventional steel structure with topsides weighing 7,600 metric tons and a steel jacket of 6,000 metric tons installed on Block 30/10a in 103 m of water. It had produced 30 billion cu m of gas during 10 years, with production exported through the Frigg complex.
Esso originally proposed to topple the platform and use it as a fish reef, said the ministry. Future responsibilities would be transferred to the state.
"Due to the uncertainty connected with leaving the installation in place, government did not consider this a viable option in the case of Odin," the ministry said. "This does not, however, rule out the possibility of offshore disposal in the future."
Karl Otto Gilje, chief executive officer of Esso Norge, said, "The plan we presented in March last year was well researched and contained a careful analysis of all practical alternatives.
"While we made our preference for the artificial reef alternative clear, the review process was rigorous and consistent with national and international rules governing platform decommissioning."
Esso let contract to a joint venture of Aker AS of Oslo and Saipem SpA of Milan for removal and disposal of Odin platform. Recycling and scrapping work will be carried out at Aker's Stord yard in Norway.
Esso said the ministry's plan will be submitted to Storting, the Norwegian parliament, for approval in the spring. Following Storting's decision, offshore lifting by Saipem is expected to begin later this year.
An Esso official said Aker has completed preparatory work for removal of the platform, including welding in place of lifting ears, to enable removal by Saipem's S7000 heavy lift vessel.
Aker and Saipem set up an alliance in autumn 1994 in anticipation of growing demand for abandonment work. This is its first contract.
Saipem will remove the platform and ship it to a new yard at Eldoeyane near Aker's Stord yard in Norway for recycling and scrapping.
Aker Offshore Partner unit will be responsible for project management and engineering. Aker Project Manager Petter Rune Larsen said the abandonment plan calls for the platform to be dismantled exactly as it was assembled but in reverse order.
"The five modules will be unhooked and loaded onto the S-7000," Larsen said. "Once they are all in position, the ship will sail to the new facility to unload its cargo for storage. Aker is currently working on opportunities for reusing the modules and equipment from the platform in new projects."
Aker said the jacket will be cut up into five sections and transported to Aker Stord in two consignments. The contractor has subcontracted hazardous waste handling to Sunnhordland Interkommunale Miljoeverk, while Aker Elektro will dispose of electrical equipment.
Brent spar
Shell-Esso continues to study other means to dispose of Brent spar, currently moored in a fjord near Stavanger. It is said to have decided against another attempt to dump the loading buoy at sea.
Meanwhile, U.K. government is keen to claim that deepsea dumping is still an abandonment option despite environmental protesters' disruption of the Brent spar dumping operation last year.
U.K. Industry & Energy Minister Tim Eggar said, "Our policy on decommissioning redundant oil and gas structures remains the same. Each case is considered to establish the best practicable environmental option to safeguard the interests of the environment and other users of the sea.
"In the Leman BK case Shell has concluded and government agreed, the best option is to bring it ashore. Most redundant North Sea installations are likely to be treated in the same way. For larger, heavier installations in the northern parts of the North Sea, deepsea disposal will remain an option on environmental and technical feasibility grounds."
Shell Expro has given its first public hint that onshore disposal is more likely.
Graham Dunlop, senior project engineer on the Brent spar decommissioning project, told an Institute of Petroleum conference the spar posed unprecedented challenges for Shell and an opportunity to learn and change.
"The spar is like an iceberg," Dunlop said. "Most of its bulk, mainly the six huge storage tanks, is beneath the water's surface. At 14,500 metric tons, its huge tanks displace 66,500 metric tons of water. Apart from the waters north of Orkney, most of the U.K. North Sea is too shallow to accommodate it.
"Herein lies the fundamental issue. Removing the spar from the water or just raising it higher without posing undue risk to people or the environment requires an exceptional feat of civil engineering."
Dunlop said that while the spar is robust and still fit to act as an oil storage buoy, calculations have shown that the original construction process, an exceptional feat of engineering in its time, cannot readily be reversed.
"Raising it out of the water in its vertical position or attempting to rotate it to the horizontal pose a significant risk to its structural integrity," Dunlop. said
"This is mainly due to its design and the need to maintain, during movements of this kind, the balance of internal and external pressures that stop the tank walls from buckling and imploding.
"This challenge is further complicated by the fact that two of the spar's six storage tanks were damaged during operation. Any future solution will have to balance benefits carefully with these risks."
Shell said last summer's outrage over deepsea dumping plans had arisen from a deeply-rooted belief in the principle of "clean seas." The company said 20 contractors will be asked to propose new disposal options, bearing in mind that U.K. government's insistence that the best environmental option "...remains deepwater disposal until demonstrated otherwise."
Dunlop said the two main dismantling alternatives for the spar involve either raising it gradually out of the water in its vertical floating position, so that cross sections can be cut off and removed to a barge, or rotating the spar onto its side so that it can be lifted horizontally onto a barge for removal to shore.
"Both options would need to address the unique challenges of sustaining the structural integrity of the installation," Dunlop said. "The safety implications of the time and labor intensity of such operations will be a vital consideration in the best practicable environmental option assessment.
"Alternatively, some sort of reuse option is attractive. In Norway, for example, decommissioning proposals for other installations have found considerable support for reusing parts of them for harbor facilities or in fish farm developments."
Shell acknowledged that technical compliance with government rules is not enough to win public favor for decommissioning plans. It had undertaken an unprecedented amount of consultation with its second plan for disposal of Brent spar in a bid to gain public trust.
Dunlop said, "The measures we are undertaking to achieve this in our search for a solution for Brent spar will, I believe, become increasingly characteristic of the way business is done in today's society. In the future, I believe Brent spar will be seen as a forerunner of many things quite beyond what it already represents in the context of decommissioning offshore installations."
A Shell official said the company is very close to completing its "long list" of 20 contractors that will be asked to submit proposals for disposal of the buoy.
"This list will be whittled down to six to submit detailed disposal plans," the official said. "It probably will be first quarter 1997 before the new disposal plan goes to government."
Heather
The next Greenpeace onslaught could erupt when Unocal U.K. Ltd. attempts to abandon its Heather platform. Despite Shell's experience with Brent spar, Unocal announced in March a controversial plan for Heather.
Heather's drilling, production, and quarters platform measures 236 m from seabed to top of derrick and has topsides weighing 12,200 metric tons and a 17,300 metric ton steel jacket.
Unocal has said it plans a partial removal of Block 2/5 Heather platform in a 㿊-50 million ($45-75 million) decommissioning program. This will involve removal of most of the topsides and toppling much of the jacket to yield clearance of at least 55 m below sea level.
"The remainder of the platform, most of which has been in the marine environment for the last 20 years, will be decommissioned safely by controlled toppling-that is, lifting and placing on the adjacent seabed-with little or no environmental impact," Unocal said.
"The total removal option was extensively evaluated. Operational complexities associated with this method result in higher exposure to safety hazards for our workforce.
"Furthermore, total removal does not eliminate environmental impacts. Overall, total removal results in onshore impacts, achieves little additional environmental benefit, results in higher exposure to safety hazards, and escalates costs to at least 䀁 million ($127.5 million)."
Heather went on production in 1978. The field currently produces about 7,500 b/d of oil, but continued production is not expected to be viable beyond the end of 1998.
"We know Greenpeace is totally opposed to this approach to decommissioning," said a Unocal official, "but our viewpoint is that whatever we leave behind will be clean steel."
Unocal will be ready to submit an abandonment plan to DTI in the third quarter, but submission cannot occur without DTI publishing its decommissioning requirements first.
A Unocal official said it would take 2 years for a complete decommissioning program.
Unocal hopes to prolong the platform's life. The company was awarded an exploration license for Block 2/4 in 1995, which holds Unocal's West Heather prospect. If this proves to be a commercial find, Heather platform could handle its production.
NW Hutton/Maureen
Amoco (U.K.) Ltd. is expected to stop production from Northwest Hutton field in Block 211/27a about 1998. The company has not proposed an abandonment plan. It has said it is working to extend production for as long as possible.
Phillips U.K. operates Maureen field in Block 16/29a, where water depth is 96 m. The field is producing through a steel platform and a short pipeline link to a tanker loading column.
Phillips said the Maureen platform is unique because it was designed to be floated off its site for deployment in another field when Maureen is depleted.
The platform's triangular gravity base, with three massive tanks, was the world's first steel platform to combine flotation, ballasting, and oil storage.
Two studies show the platform can be refloated, and it is said to have enough working life remaining to be reused on its own or as part of a larger development scheme.
Phillips is trying to find a buyer. In case a buyer cannot be found, the company also has invited tenders from contractors for onshore disposal and recycling.
Issues unresolved
While Norway's government appears to be against dumping of platforms while not ruling it out in theory, the U.K. government continues to support inclusion of dumping as a valid option.
In this year's newly published Energy Report, an annual review of the entire U.K. energy industry, DTI hinted it may make life difficult for Shell Expro as it seeks approval for a new disposal plan for Brent spar:
DTI said, "The government will consider any suggestions put forward by Shell, but any new proposals will need to address those issues which had originally led to the conclusion that deepsea disposal was the best option."
Following the media hammering the U.K. oil industry took after the Brent spar fight, the U.K. Offshore Operators Association appointed a public relations firm to publicize its plea for a scientific approach to abandonment rather than an emotional response as demonstrated by the antidumping campaign.
Paul Horsman, head of Greenpeace's international oil campaign, said, "It is disappointing to see that the industry's response in the U.K. has been simply to see the issue as a PR battle, and all they have to do is convince the public by more glossy leaflets and adverts.
"This is not the response we want to see. It is negative and looks backward and not forward. The challenge to industry is to accept the situation that dumping redundant installations at sea is not acceptable and to start to work to find the best solutions with us. We do not mind cheap solutions as long as the environment is protected."
Rick Le Coyte of Greenpeace's U.K. oil campaign said that since Brent spar issue erupted, no company has gone further than timidly suggesting that disposal of platforms at sea is a preferred option.
"We will continue to campaign against dumping at sea of any industrial waste," Le Coyte said, "and that includes oil and gas installations."
Meanwhile, U.K. operators await DTI platform abandonment guidelines, which are scheduled to be published this year.
A DTI official said that since draft guidelines were published more than a year ago "...other things have had to be considered."
The official said DTI has received lots of advice on many topics, including the Brent spar experience, and guidelines are taking longer than expected. They should be ready for publication in late summer.
Tim Eggar, U.K. industry and energy minister, last month reported publication of a report on abandonment he had commissioned from the Natural Environment Research Council.
Eggar said, "I welcome the conclusion of the report that the global impacts on the environment and on human health of the sea disposal of a structure such as the Brent spar would be very small-roughly equivalent to the impacts associated with the wreckage of a fairly large ship."
Given the U.K.'s recent bungled response to the grounding of the Sea Empress tanker off South Wales, which spilled 70,000 metric tons of crude oil, these are hardly words to reassure a public highly sensitive to the issue of platform dumping.
Copyright 1996 Oil & Gas Journal. All Rights Reserved.
