Making the Most of your Offshore Infrastructure – Asset Life Extension

Making the Most of your Offshore Infrastructure – Asset Life Extension

Making the Most of your Offshore Infrastructure – Asset Life Extension

In the world's oceans, oil and gas platforms have stood on their jacket foundations for many years. But there is an ongoing silent battle against time and the relentless forces of nature. These offshore assets face the inevitable wear and tear of years spent in a highly corrosive environment and battling the elements.

When existing assets approach the end of their designed lifespan, the need for innovative solutions to extend their longevity becomes paramount. FoundOcean specialises in precisely that – breathing new life into ageing structures through comprehensive SMR interventions.


Why do offshore assets need life extension solutions?

There are different reasons why an asset may need to undergo strengthening, modification or repair intervention:

  1. Findings from routine inspections can uncover damage or fabrication defects requiring repairs.
  2. There is a need for additional conductors.
  3. A field is going to continue production after its original intended design life.


Common issues faced by offshore structures include:

  • Corrosion of members and/or joints
  • Fatigue damage
  • Dented members
  • Need for increased fatigue life
  • Life extension requirements


Understanding the Need: Ageing Infrastructure in Key Regions

This is affecting jacket foundations for number of assets in the North Sea, the Mediterranean and the Gulf of Mexico. All are facing similar challenges, highlighting the global significance of the issue. Assets in the Gulf of Mexico were designed with hurricanes in mind, whereas, for assets in the North Sea, fatigue due to wave loadings has been much more of a priority.

Many of these assets are now decades-old and the industry’s understanding of environmental loads is much better now than it was when these assets were being constructed.


Design code updates

Lessons learned over the years have shown that design codes have needed updating. For example, the wave loads which offshore installations need to withstand have increased, in some cases quite dramatically. Other loading parameters and marine growth allowances are also better understood now, leading to design code updates.


Design errors

Errors could include missed critical loads or load combinations (such as overlooked transportation fatigue, incorrect structural modelling or poor detailing). ‘In the old days’, the method of referencing structural designs from other regions also resulted in design errors, with primary loadings being distinctly different between, say, the Gulf of Mexico and the North Sea.



Fatigue would typically take the form of cracks at the end of members where they frame into joints. The design of early jackets was heavily dependent on experience in the Gulf of Mexico. In the North Sea, such designs are unable to withstand the 6 million wave loadings per year. Many structures – or their components – have required fatigue damage repairs, or to be strengthened to prevent anticipated damage.



General excessive corrosion can result from an under-designed or failed cathodic protection system, but localised corrosion can also occur. For example, there could be galvanic corrosion – as is the case when carbon steel caissons house stainless steel components, whereby thinning or perforations of the carbon steel can occur.



Jackets can be damaged during loadout, transportation and installation, resulting in  weakened welds or dented members. Once in situ, heavy objects dropped overboard or ship impacts can result in bent or buckled members, or crack developments at member/joint connections.


Fabrication defects

Errors may have occurred when, for example, welds were poorly made or were misaligned, steel properties were non-specification, or construction access was tight.

All of these details could have contributed to over-stressed members and joints.


FoundOcean's Tailored Solutions: A Closer Look

FoundOcean offers a range of SMR solutions designed to address the unique needs of different weaknesses – or potential weaknesses - of offshore assets.


Member Infill and Jacket Strengthening

We specialise in reinforcing jacket foundations through our advanced grouting techniques.

Grouting a member offers the advantage of not increasing member diameter, so therefore no impact on wave loading.

This could be carried out for one or more of the following reasons:

  • to increase axial compressive (squash) strength of the member
  • to improve overall member stability and resistance to buckling
  • to improve strength or reduce the stress concentration factor (SCF) at a tubular joint chord.

Filling a member with grout gives it incremental compression loading capacity.

This technique is also ideal for members in vulnerable areas (eg adjacent to boat landings) to resist local damage.

Filling joints with grout leads to reduced chord wall deformations and results in increased fatigue resistance.

Filling the annulus between a pile and leg with grout forms a double skin member with increased strength and fatigue resistance at incoming brace connections.

Each of these techniques will bolster structural integrity, mitigating the risk of corrosion and fatigue. By extending the lifespan of these critical components, operators can extract maximum value from their investments while ensuring operational reliability.



There are many types of structural clamp. Some are designed specifically to carry load whereas others are to provide stability. If a tubular member requires strengthening, there are various clamping options. A clamped connection is typically fabricated in two sections, split to accommodate installation around an existing member or joint.


Unstressed grouted connections

The annular space created by the clamp is filled with grout. Bolts are fully tightened beforehand so that the grout/steel interface is not stressed. Grout allows for larger annular tolerances along damaged or imperfect members, enabling even load transfer along the repair. The takes place via bond and interlock between the grout/steel interface. Often a long connection is necessary to generate sufficient load transfer capacity.


Stressed mechanical clamps

This provides a connection between two concentric tubulars and relies on the friction capacity of the interface between the two tubulars for load transfer. The outer saddles are stressed together to generate a force normal to the friction surface. This is created through long bolts which apply load to the saddle halves which produce friction grip onto the base member.


Stressed grouted clamps

This is a hybrid of the unstressed grouted connection and stressed mechanical clamp. Cementitious material is poured into the annular space between the tubulars. Once it reaches a predefined strength, an external force is applied by tightening the long stud bolts holding the casings together, stressing the grout. Base member obstructions – such as weld beads or small doubler plates can be accommodated within the grout annulus.

The strength of a stressed grouted clamp comes from a combination of plain pipe bond and grout/steel friction that develops from compressive radial stress at the grout-to-tubular-member interface.

Stressed grouted clamps exhibit high strength-to-length ratio. Combined with its ability to absorb significant tolerances, this repair technique is very popular.


Stressed elastomer-lined clamps

Much like the stressed grouted clamp in design, here the inside of the clamp saddle is lined with an elastomer material, creating a friction-based connection. The long studbolts holding the casings together are then tightened, stressing the connection.

The strength of an elastomer-lined clamp is significantly lower than that of a stressed grouted clamp, due to the low stiffness of elastomer lining compared to that of steel.


In conclusion

Offshore work, particularly subsea work, can be expensive and risky, and our key objective is to ensure ease of installation and minimum offshore working time, with safety being paramount at all times.

Being a proud member of the Venterra Group means we can call upon the services of our sister company, Gavin & Doherty Geosolutions (GDG), if their expertise is required in the analysis and design stages of an SMR project.

Our solutions cater to the evolving needs of offshore assets, enhancing their performance and longevity. By addressing issues proactively, we can help operators to avert potential difficulties or disruptions to supply, and prolong the lifespan of their infrastructure. By safeguarding their subsea infrastructure, operators can maintain peak performance and extend asset lifespan in the most demanding environments.


FoundOcean reinforces not just the structures themselves but also the foundation of a more sustainable future for offshore operations worldwide.