Decommissioning & Repurposing
Our Global Business Development Manager, Paul Burns, takes a look at the scope and scale of oil and gas decommissioning around the globe.
Introduction
As many of the world’s 12,000+ offshore oil and gas fields mature, decommissioning is becoming an increasingly critical process which must be completed as safely and sustainably as possible. Here in the UK, where we are headquartered, the Offshore Energies UK Report 2024 demonstrates how decommissioning activities are ramping up, with both spending and the actual number of structures and pipelines being decommissioned each year more than doubling.
So, what happens to retired oil and gas infrastructure?
- Dismantling and recycling: an incredible 97% of the Brent Delta platform was recycled when it was dismantled in 2017.
- Leaving in place: instead of fully dismantling, making structures safe and leaving them in situ.
There is much discussion about what should be done with abandoned rigs. In the Gulf of Mexico and Malaysia, some of these structures have been turned into man-made reefs for diving. The UK government has also suggested that legacy oil platforms could be utilised in the production of green hydrogen.
Both methods – fully dismantling or leaving some structures in place – pose issues. While some equipment can be repurposed or relocated to reduce waste and support the energy transition, the decommissioning and removal of infrastructure remains a costly, lengthy and disruptive process. The argument for leaving infrastructure in place is strong – it’s substantially cheaper and often less disruptive to the established habitat. But, without proper management, abandoned sites could be a maritime hazard and pose the risk of contamination, potentially causing long-term environmental damage.
The Global Picture
Across the world, decommissioning is still relatively in its infancy. That said, more than 70% of current global oil and gas production comes from mature fields which will soon reach the end of their lifecycles. Therefore, in the next decade, decommissioning will become the O&G sector’s biggest challenge. For instance, in the Gulf of Mexico alone, according to a 2024 report from the US Government Accountability Office, there are almost 3000 wells and 500 platforms already overdue for decommissioning.
FoundOcean has already gained a great deal of experience working on projects in the North Sea. This means that we are now well positioned to roll out these projects internationally, including those managed by FoundOcean Inc. in Houston, Texas. We also have a new equipment base in Taiwan, and we are supported by our worldwide team who can discuss decommissioning projects anywhere in the world.
The North Sea
Much of the completed decommissioning work so far has been in the North Sea. This region has some of the oldest oil and gas assets globally, dating back to the 1970s, and therefore many wells and rigs have already reached the end of their lifecycle. This means that decommissioning expertise in our part of the world is more advanced than anywhere else. In the next 30 years, almost all of the O&G infrastructure in this region will require decommissioning. The majority of structures are production platforms with either gravity-based concrete foundations or jacket foundations. There are estimated to be over 5,000 wells and 3,000 interconnecting pipelines in our North Sea waters.
Decommissioning Options
The decommissioning process begins with the "plug” phase, when oil wells are permanently sealed to prevent any leakage. Then attention shifts to the removal of surface structures, which can be either completely taken down to the seabed or, increasingly, decontaminated and left in place to serve as artificial reefs that will support marine life.
In the North Sea, when infrastructure is left in situ, there are several criteria set out by the Department of Energy and Climate Change (DECC) which must be satisfied:
- Concrete structures require vertical illumination above water level
- Vertical structures are removed to at least 55 metres below sea level
- Remains are marked with necessary aids to navigation
- A 500-metre zone around any platform and 100 metres around pipelines must be debris-free
Our Techniques
When infrastructure is to be fully removed, FoundOcean has several techniques to secure the safe removal of frameworks and provide a permanent seal. We can clean and seal live systems or plug obsolete systems to meet all local or global regulatory requirements.
Cleaning and Displacement
For most projects, one of the main aims is displacement of oil residue as this mitigates environmental concerns, substantially reduces any pollution risks and has a positive economic impact. We use customisable low-density fluids but can use a wide variety of chemical additives for temporary flushing or permanent displacement of oil-filled pipelines.
Lift Point Installation
We can manufacture and install custom-fit lift point reinforcement for both “top down” lifts by crane or “bottom up” lifts by vessel, all engineered to meet the required strengths for safe removal of structures.
Leg Capping
By installing custom formworks and filling legs or other members, we can provide permanent isolation, preventing pollution and minimising the impact of the decommissioned structure on the surrounding marine environment.
Leaving in Situ
Displacement and Sealing
In 2022, for a decommissioning project where part of the structure and pipeline was staying in place, we developed a system for displacement and sealing ‘all in one’. We created a proprietary, low-density, silicon-based elastomer to pump into the rundown lines. This displaced the oil into the storage cells before the material set.
The method was so successful that there was no requirement for any follow-up work. The gel-like substance we added to our cementitious mix enabled enhanced oil recovery at the same time as permanent sealing and saved our client both time and money.
Member Infill / Strengthening
Our infill technique allows for both asset life extension through reinforcement, or structural reinforcement of jacket members for removal.
Brent Bravo Decommissioning
The Brent Field, situated in the North Sea near the Shetland Islands in Scotland, was one of the largest oil and gas fields in the UK, brought into production in 1976 and reaching the end of its lifecycle in 2006, when all production ceased and it was assigned for decommissioning.
The Brent Field was made up of four platforms: Alpha, Bravo, Charlie and Delta. The decommissioning project was on a significant scale and had to be approached carefully so as to minimise any environmental impact to the surrounding area.
Each of the three gravity base structures at Bravo, Charlie and Delta weighed approximately the same as the Empire State Building, a mighty 300,000 tonnes. The topside platforms alone were 25,000 tonnes and had to be removed from the concrete legs to be floated ashore for recycling.
Brent Bravo, the second platform. was decommissioned in 2017, a project in which FoundOcean played a significant part. We developed a special concrete blend to construct six reinforced concrete blocks that could support the lifting of the topside platform.
We first conducted a series of trials onshore in order to create the grout mix and calculate the correct hydration temperature, strength and density. Our analysis proved the concept for the grout and addressed ‘heat of hydration’ concerns for the large pour dimensions that were required.
FoundOcean also designed and installed a modular shuttering system for the lifting block formworks, and installed and fixed the reinforcements within the cramped confines of the topside’s labyrinthine rooms and corridors. During this project, we mixed more than 800 tonnes of dry grout material in a large super pan mixer whilst offshore.
Ultimately, the entire platform was removed in a single 9-second lift by Allseas’ Pioneering Spirit, in order to be transported onshore for recycling. The video is well worth a watch.
Brent Bravo had been constructed with stability in mind and the topside platform was never originally designed to be lifted from underneath. Achieving this as a single lift was an amazing feat of engineering.
Conclusion
As the global offshore oil and gas industry moves toward widespread decommissioning, the challenge of safely and sustainably retiring infrastructure continues to grow.
While complete removal and recycling remain the most common approaches, alternative solutions – such as repurposing structures for marine life or energy transition projects – are gaining traction.
FoundOcean’s extensive experience in the North Sea has positioned us at the forefront of this evolving industry, allowing us to develop innovative techniques that improve efficiency, save our clients money, reduce environmental impact, and ensure compliance with global regulations.
With decommissioning set to become a defining challenge for the O&G sector in the coming decades, expertise and innovation will be key to delivering safe, cost-effective and sustainable solutions worldwide.
For more information on FoundOcean’s experience and capabilities, contact the team on +44 1506 440330 or email info@foundocean.com