August 2023
Special focus: Offshore operations

Decommissioning contract activity remains steady, concentrated in Europe

Global offshore decommissioning work continues at pace, with a significant portion occurring on the UKCS. Meanwhile, technical advances related to decommissioning continue, as well.
World Oil Staff / World Oil

Given the emphasis in some countries and regions on achieving net-zero production and/or facilitating the transition to non-carbon energy sources, it is no surprise that there is a steady flow of offshore decommissioning contracts. The decision to decommission offshore facilities takes into account their age, productivity and maintenance required, as well as the energy policies/inclinations of various countries.  

Accordingly, this article provides a collection of recent contracts either announced or completed, to provide a representative slice of overall activity. Also included is a look at several technical innovations announced in recent months.  


The UK has a healthy share of the world’s offshore decommissioning work at present. What follows is a representative group of recent project announcements or completions. 

Amethyst field platform removal. In early May, topside skidding in the decommissioning of the A2D platform, Amethyst field, UKCS, was completed. Operator Perenco, along with Petrodec, the decommissioning services specialist, announced on May 5 that the A2D platform topside had been safely removed for final dismantling. The operation was conducted successfully, using Petrodec’s patented “skidding” technique, which was deployed by its dedicated jackup, the ERDA, in the southern North Sea, Fig. 1. With a weight of 1,179 tons, this was the heaviest Amethyst topside to have been removed so far.  

Fig. 1. The A2D platform topside was removed safely for final dismantling, using a patented “skidding” technique. Image: Petrodec.

The complete scope of the A2D decommissioning project was achieved with Petrodec, an affiliate of the Perenco Group, having been granted operator status by the UK NSTA on behalf of Perenco UK, Fig. 2.  

Fig. 2. In working on the A2D decommissioning project, Petrodec was granted operator status by the UK NSTA on behalf of Perenco UK. Image: Petrodec.

This project was another milestone on Amethyst field, and it follows the Hydrocarbon Safe (HCS) Campaign on all platforms and brine flushing of intra-field and export pipelines, the plug-and-abandon of all platform wells, and the removal of C1D, B1D and A2D topsides with a combined total topsides weight of 2,900 tons. Final operations to remove the topsides and four steel jackets of platform A1D are scheduled from January 2024.  

Amethyst field was one of the later-life assets acquired by Perenco from BP in 2012 as part a package of SNS assets. Perenco subsequently consolidated its position to 100% on Amethyst by acquiring the participating interests of Centrica and Murphy Oil in licences P.005, P.030, P.050 and P.133. Amethyst consisted of four conventional fixed jacket wellhead structures, with helipads and cranes installed and brought into production between 1989 and 1991. Platforms A1D, A2D, B1D and C1D had six or nine slots, and six or seven producing wells. The field stopped producing in 2020, following which Perenco UK started the application for decommissioning operations in collaboration with Petrodec.  

“The successful and safe skidding operation to remove the heaviest topside to date exemplifies Petrodec’s technical ingenuity as a decommissioning specialist, bringing together the technical expertise of a contractor and the reliability of a decommissioning operator, said Petrodec General Manager Rainier Verhulst. “It also clearly highlights Perenco’s integrated approach to late-life assets, first extending the production lifespan of assets by operational efficiencies and investment, then developing innovative and fit-for-purpose solutions to safely decommission the facilities. I would like to thank all of those involved.”  

P&A work in Balmoral area. May 22, Expro secured a new contract with operator Harbour Energy for a well abandonment campaign as part of the decommissioning project for the Balmoral area, on the UKCS. The multi-year contract, valued at more than $20 million, will utilize Expro’s Subsea Well Access technology (Fig. 3), with a combination of open-water and in-riser applications deployed from a semi-submersible rig. 

Fig. 3. As part of a well abandonment campaign within a decommissioning project for the Balmoral area, Expro is utilizing its Subsea Well Access technology. Image: Expro.

Wells that require abandonment tend to suffer from loading and fatigue issues on the wellhead and Xmas trees. Expro’s ability to supply a lightweight open-water system will help to mitigate these loading issues during the subsea well access intervention part of the overall abandonment campaign. The firm’s open-water and in-riser bore selector technology, which eliminates the use of a dual-bore riser for the entire abandonment campaign, is designed to deliver significantly reduced system deployment and retrieval times and with lower maintenance costs. 

To overcome key technical requirements from the customer, Expro devised an innovative technological solution, based on a newbuild, lightweight intervention system, incorporating its unique subsea ball valve technologies. The company’s existing API 17G standard, high-debris ball valve was recently qualified to provide a single-ball cut-and-seal on coiled tubing. This ball valve technology will be re-packaged into bespoke open-water riser housings to provide the lightweight solution required. 

The solution developed for this award expands Expro’s subsea well access portfolio and allows the company to now supply the client with all subsea well access tooling required for the abandonment campaign in the Balmoral area, for horizontal and vertical Xmas trees. 

This contract award further extends Expro’s involvement in this major campaign. The firm’s Well Test and Well Construction teams were already supporting the project. It will be delivered from Expro’s Aberdeen facilities. 

“We are proud to have secured this award by offering an innovative approach to meet the needs of this important customer,” said Expro V.P. for Europe and sub-Saharan Africa, Colin Mackenzie. “We are delighted to further extend the scope of our partnership on this campaign which reinforces our position as a key enabler within the plug and abandonment market.” 

Schooner platform removed, discarded. Norwegian operator DNO ASA reported on June 5 that the wellhead platform production facilities had been removed from Schooner field, offshore the UK. This was the last major offshore operation under DNO’s multi-year North Sea decommissioning program. 

The heavy lift was conducted using Heerema Marine Contractors’ Thialf semi-submersible crane vessel, Fig. 4. The 1,200-tonne platform deck was lifted aboard the vessel on May 17, while the jacket was removed on May 23 after the piles had been cut 3 m below the seabed. The deck and jacket were then transported to Hoondert Yard in the Netherlands for dismantlement and recycling. 

Fig. 4. To remove the wellhead platform from DNO’s Schooner field, offshore the UK, a heavy lift was conducted using Heerema Marine Contractors’ Thialf semi-submersible crane vessel. Image: DNO AS.

“We have conducted these operations in a safe, cost-efficient and environmentally responsible manner, coordinating five tier-one contractors and displaying our capabilities as a full life-cycle offshore operator,” said DNO Chief Operating Officer Chris Spencer.    

In 2019, DNO assumed operatorship and working interest in Schooner and Ketch fields on the UKCS and Oselvar subsea field in Norway. These are three end-of-life fields, whose decommissioning had been deferred by the previous operator. DNO completed plugging and abandonment (P&A) of the nine Ketch wells and the three Oselvar wells in 2021, followed by the 12 Schooner wells in 2022. The Ketch and Oselvar production facilities were removed and dismantled last year. It is expected that about 95% of the removed materials will be recycled. 


While the UK may be leading in sheer number and proportion of decommissioning projects, there are a number of notable projects in other countries and regions, either underway or set to begin shortly. Here is a representative group of such projects. 

The Netherlands: ABL Group appointed to “L7 Restitution Project.” On April 17, TotalEnergies EP Nederland appointed ABL Group (ABL) as marine warranty surveyor for decommissioning operations at L7 field in the Dutch sector of the North Sea. The L7 Restitution Project includes the decommissioning of nine jackets and ten topside modules, including bridge structures from L7 field. Total weight of the installations is approximately 17,500 tonnes, Fig. 5.  

Fig. 5. ABL Group is conducting decommissioning operations at L7 field in the Dutch sector of the North Sea on behalf of Total Energies EP Nederland. The project includes decommissioning nine jackets and ten topside modules, including bridge structures. Image: ABL Group.

ABL is providing marine warranty survey services for the preparations, lifted removals, transportation and relocation to the onshore dismantling yard in Norway. ABL also will conduct suitability surveys of all the marine units that will be utilized for the project. ABL will manage the project out of its office in Aberdeen, Scotland, UK. It will be supported by ABL’s operations in the Netherlands and Norway. ABL estimates its contract value to be approximately EUR 500,000.  

“ABL Group has a long history in the oil and gas sector and vast experience with the challenges and important considerations that can impact decommissioning work,” said Ashley Perrett, ABL’s country manager in Scotland. “We are delighted to be partnering with TotalEnergies EP Nederland on the L7 project as part of our growing portfolio of work in this area.”  

Planning work immediately commenced, and offshore operations will occur throughout 2023 and 2024. The installations will be removed, using a floating sheerleg crane that will transfer cargo to a barge in sheltered waters near Den Helder, the Netherlands, for onward transit to the dismantling yard in Vats, Norway. AF Offshore Decom will manage the removal and recycling of the installations.  

“Decommissioning of oil and gas fields is a complex task,” said Nicholas Kaczynski, ABL Group’s project manager for the L7 decommissioning project. “As a non-productive cost, we fully appreciate the importance of identifying the correct solution to ensure cost-efficiency without compromising safety and quality.”  

L7 field was one of the first major offshore gas fields on the Dutch Continental Shelf. Initial discovery occurred in the late 1960s, and development of various reservoirs took place throughout the 1970s and 1980s. From 15 production wells, the field produced over 21 Bcm of natural gas (~140 MMboe) with a recovery factor of > 80%. After 40 years of operation, the facilities ceased production in 2017.  

ABL is part of Oslo-listed ABL Group ASA, an independent energy and marine consultancy group to the global renewables, maritime and oil and gas sectors.  

UAE-Abu Dhabi: Multi-well decommissioning contract awarded. Aquaterra Energy announced on June 27 that it had received a multi-million-pound contract with a major Abu Dhabi--based operator, working in partnership with TPMC, to provide offshore riser equipment and services for the decommissioning of eight wells, in an 80-m water depth by 2028.  

Aquaterra Energy secured the tender through its offshore engineering expertise, regional knowledge, and status as a fully independent riser connector OEM. The offshore specialists will provide a completion and workover riser system, complete with AQC-CW connectors, as well as an additional subsea riser system, tie-back engineering and rig modifications. Throughout the contract, Aquaterra will deliver a complete end-to-end managed service, providing engineering services, expertise and personnel.  

The completion and workover riser system, complete with AQC-CW connectors, is certified to BS EN ISO 13628-7 2006 and can operate in water depths as great as 1,500 m. The system has been designed to withstand repeat make-and-breaks, while offering a gas-tight metal-to-metal seal.  

Aquaterra Energy will work closely alongside in-country partners to manufacture and transport the project equipment. This will provide thousands of hours of local employment for the region, as well as opportunities for upskilling and knowledge-sharing. Local in-country inspectors will be deployed to ensure the high quality of work throughout the project. By working with local partners, Aquaterra will ensure significant carbon savings through minimizing transportation and travel costs. 

“Winning this tender further demonstrates our team’s global riser system expertise, understanding of operational requirements in the Middle East, and the significant advantages of our independent connector OEM status,” said Aquaterra’s Operations Director, Andrew McDowell. “We’re looking forward to utilizing our experience and working closely alongside engineers in the UAE, sharing our knowledge, and building on existing local capabilities to deliver a top-class end-to-end service.” 

Australia: DTM buoy decommissioning contract offshore Western Australia. On July 10, McDermott said it had been awarded an engineering, procurement and removal contract for offshore decommissioning work by Woodside Energy. The award is for full removal of the Stybarrow disconnectable turret mooring (DTM) buoy, as part of the decommissioning of Stybarrow field in the northwest Cape of Western Australia. 

Under the contract scope, McDermott will provide project management and engineering services for the recovery, transportation and offloading of the DTM buoy to a suitable onshore yard facility for dismantling and disposal. "This award not only demonstrates McDermott's proven track record in undertaking deepwater projects of diverse scopes, but it also highlights the critical importance of decommissioning in the offshore industry," said Mahesh Swaminathan, McDermott's Senior V.P., Subsea and Floating Facilities. "With our seamless integration of engineering, fabrication, and offshore mobilization expertise, we believe we are well-equipped to execute this project efficiently and responsibly, ensuring the safe recovery and removal of the Stybarrow DTM buoy." 

McDermott's Perth-based team will oversee project management, while engineering and fabrication support will be provided by the team in Kuala Lumpur, Malaysia, and Batam, Indonesia. The DTM buoy will be lifted and removed, utilizing McDermott's DLV2000 vessel. 

Australia: Major contract for FPSO decommissioning offshore Northern Territory. On July 11, global energy consultancy Xodus was awarded a contract to provide technical and project support services for Phase 1 of the decommissioning of the Northern Endeavour FPSO. This specific phase of decommissioning covers activities to facilitate the disconnection and removal of the FPSO, including topsides and subsea flushing and well suspension. 

Xodus is working on behalf of the Australian government, providing advice on project coordination, regulatory and environment, health and safety, technical, quality assurance, and contract management as part of the agreement. 

Alasdair Gray, Late Life and Decommissioning lead at Xodus said, “We have a highly experienced local team, with several of our colleagues having extensive experience of the Northern Endeavor, either from the early design and installation phase of the project or during production operations. This means that whilst being able to bring a fresh approach, the facility is already familiar to much of the team. We understand environmental sensitivities and the impact these can have on any proposed activity or execution plan. Expert technical advice and careful planning will be critical to the successful decommissioning of the offshore field in a safe and responsible manner. We are pleased to provide the necessary support to ensure that the decommissioning strategy is robust and ultimately compliant with regulatory expectations.” 

A spokesperson for the Department of Industry, Science, and Resources (DISR) Phase 1 NE Decom Project Management Team commented, “We are pleased that Xodus has officially joined as our assurance team for Phase 1 of the Northern Endeavour Decommissioning Project. This marks a significant step forward in our role in managing the environmentally responsible and safe closure of the Northern Endeavour FPSO, permanent plugging and abandonment, and remediation of associated fields. We value Xodus’ forthcoming contributions and look forward to a collaborative and productive partnership.” 

The Northern Endeavour is a 274-m long FPSO, which is permanently moored between the Laminaria and Corallina oil fields in the Timor Sea. It stopped producing oil in 2019. In non-production mode, the now redundant production system (Fig. 6) comprises a network of subsea wells tied back to the permanently moored vessel unit through a system of subsea manifolds, flowlines, umbilicals, and dynamic risers. Produced oil was stored onboard the vessel and unloaded via offtake tankers using a tandem mooring system. 

Fig. 6. Although not in production for four years, the Northern Endeavour FPSO has been moored between Laminaria and Corallina oil fields in the Timor Sea. In decommissioning the FPSO, Xodus and other firms must contend with a network of subsea wells tied back to the vessel unit through a system of subsea manifolds, flowlines, umbilicals, and dynamic risers. Image: Xodus.

The decommissioning follows the liquidation of the owner of the Northern Endeavour, the Northern Oil and Gas Australia (NOGA) group of companies, in 2020. A temporary levy on offshore oil production is recovering the full costs of decommissioning and remediating the Laminaria and Corallina oil fields. 


In addition to the ongoing decommissioning projects, the industry continues to generate new technical innovations related to these efforts. These technologies relate either to decommissioning directly or to the harnessing of facilities already decommissioned for new purposes. The following items are a representative slice of such innovations.  

Investment committed to launch largest subsea Chopsaw. Decom Engineering (Decom) has invested more than £1 million to develop its largest Chopsaw to date, in response to client demand for larger-sized subsea pipe-cutting capability, Fig. 7. The C1-46 Chopsaw has been designed to cut tubulars and other materials up to 46 in., and its innovative design is able to cut a wide range of materials, including inconel alloys, duplex and concrete. 

Fig. 7. Decom Engineering has made a significant investment to develop its largest Chopsaw to date, in response to client demand for larger-sized subsea pipe-cutting capability. Image: Decom Engineering.

It can be operated in water depths as great as 2,000 m and is currently deployed on its first project on behalf of a global energy company on a UK North Sea workscope. That project involves cutting large surface-laid pipelines (36 in.) with 57-mm concrete coating, along with other large pipelines.  

With the ability to cut in any orientation, the C1-46 is capable of multiple cuts per blade (20-100), resulting in large cost-savings and increased efficiency. Blade changes are efficient and safe, and the Chopsaw can be supplied in a number of configurations and settings to suit project requirements. 

Multiple lifting points around the tool allow a highly versatile angle of deployment, and an array of cuts can be completed while subsea or held in wet storage, without returning to the surface. The tungsten carbide-tipped saw, which can be operated topside or by ROV (with hot stab capability), is highly adaptable to suit challenging surroundings and varied structures. 

“…making this significant investment to bring the C1-46 Chopsaw to market was a result of clients indicating they would welcome larger sized cutting options, as this is an area existing technologies struggle with,” said Decom Engineering Managing Director Sean Conway. “The saw clamps are designed to penetrate into the seabed/sediment and to minimize the need for trenching.” In recent months, other Chopsaws in the C1 range have been deployed on a number of complex projects offshore West Africa, Mauritania, Gulf of Thailand, Norway and the UKCS. 

Revamped wells system aids decommissioning and transition while saving money. Decommissioning and energy transition projects offshore the UK received a significant boost following the July 7 relaunch of the North Sea Transition Authority’s (NSTA’s) digital wells database, with improved functionality and greater flexibility, Fig. 8. 

Fig. 8. The relaunch of the North Sea Transition Authority’s digital wells database, with improved functionality and greater flexibility, addresses the need to consider reusing or repurposing wells as part of the decommissioning process. System amendments will allow more accurate information on final well abandonment to be gathered and scrutinized by the NSTA. Image: NSTA.

First set up in 2002, the Wells Operations Notifications System (WONS) dealt with more than 1,100 applications in 2022, alone, relating to exploration, production, development and decommissioning. It allows a company to submit online applications and notifications for well activity and the NSTA to give those submissions proper technical scrutiny before issuing consent.  

Given that the needs of operators are changing, as they adapt their businesses to support the energy transition, WONS has been updated to assist those changing requirements. This includes, for the first time, the ability to apply to drill a wellbore specifically linked to a carbon storage license.  

There are over 12,500 wellbores in UK waters of the North Sea, with around 5,500 wells plugged and abandoned. The need to consider reusing or repurposing wells as part of the decommissioning process is now a higher priority, and the system amendments will allow more accurate information on final well abandonment to be gathered and scrutinised by the NSTA. This will allow better assessment for possible future use, such as playing a part in carbon storage.  

The system’s greater flexibility also allows users to record more detailed information on the identity and role of companies responsible for the wellbore, and also those responsible for the associated data. This will support greater compliance and provide more granular information for future reference.  

Wellbores that cross the Median Line – operating in UK and Norwegian or Dutch waters – created time-consuming difficulties in the previous system. These issues have now been resolved, saving valuable time and money for both operators and the NSTA.  

“We have updated the system with the needs of users in mind. It is now much quicker, easier to use and responsive to their real day-to-day requirements,” said NSTA Director of Corporate Nic Granger. “The more accurate and more detailed information it now collects will be very useful in making decisions about potential reuse and repurposing of wells and siting of carbon storage locations.”  

Companies awarded license to convert decommissioned UK fields into a CCS facility. Spirit Energy, with the support of majority shareholder Centrica Plc, and Stadtwerke München GmbH (SWM) was granted a carbon storage license by Britain’s NSTA on May 18. This represents a further step towards the firms’ net zero vision of repurposing the North and South Morecambe gas fields for carbon capture and storage.  

This license award places the companies at the forefront of decarbonization efforts in the UK, with the MNZ (Morecambe Net Zero) Cluster having the potential to be one of the UK’s biggest carbon storage hubs. It will be able to store up to a gigaton of carbon dioxide, the equivalent of three years of current UK CO₂ emissions. It could initially store above 5 mtpa of CO₂, scaling in time to 25 mtpa. The MNZ Cluster will be able to accept CO₂ transported by pipeline, ship and rail.   

In April, Spirit Energy submitted a qualifying Expression of Interest for the MNZ Cluster to be considered as part of the government’s Track 2 CCUS Cluster Sequencing process. The Cluster’s carbon stores will provide long-term access to a sustainable carbon storage solution for the UK’s carbon-intensive industries, helping tackle its emissions while still supporting the many thousands of reliant jobs across the UK.  

“At Centrica, Net Zero is our business, helping us deliver a decarbonized energy system,” said Chris O’Shea, Chairman of Spirit Energy and CEO of Centrica plc. “I’m delighted we’ve been awarded this license to move forward our plans for carbon capture and storage. Morecambe Bay has the ability to become a world-leading carbon storage facility and could see the creation of thousands of jobs in the North of England.”   

Spirit Energy has “ambitions” for the two gas fields to form the core of a green super-hub. This would explore opportunities that include direct air capture, manufacture of blue hydrogen, production of green hydrogen, integration of other renewable power generation facilities, and energy storage. 

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