6 May 2022

Just how feasible is it to reuse subsea assets

Participating in the circular economy can seem daunting – there’s a lot to consider if you’re looking to do the right thing and demonstrate a true commitment to sustainability. Even more so when dealing with specialist subsea equipment. But you may be surprised to learn that reuse is more achievable than you first thought.

Often, the first consideration is, how do you get your reuse business case over the line? One way is to verify that what you propose is actually possible through an independent feasibility study.

At Evolve Surplus, we specialise in subsea equipment and offer independent, third-party assessments of reuse opportunities – creating potential to market used assets to other energy operators.

Let’s break it down.

In most cases, operators have a blanket view that once subsea assets have reached their end of life, those assets are, well, finished. They’re scrap and have little, if any, residual value.

We question this assumption. Our reuse feasibility studies for energy giants such as Repsol paint a different picture—that reuse is not only possible, but beneficial.

In these studies, we conduct systematic assessments to determine whether there is a reasonable expectation for used assets to have a second life.

We start by asking questions about how the asset has been operated – when it was installed, how long it has sat on the seabed, what the original design life and residual design life is, what has flowed through it and so forth. Basics to establish the foundation of our analysis.

We identify the necessary steps to safeguard the integrity of the equipment. Can we clean and decontaminate it? What do we need to do to preserve its integrity?

We then consider what the opportunities are for its future use, and how an oil and gas development could be tailored to reap maximum benefit from reuse.

Sure, at times, new field developments or tie-backs require purpose-built equipment because of operator-specific functional and technical requirements, water depth, high pressure and/or fluid temperatures. But our analyses show that, in most cases, subsea equipment is generic enough to be used again in a variety of different settings.

In assessing equipment for reuse, we work to identify areas where the actual operating envelope may be larger than the original technical specification. It could be, for example, that the field requires a 100 degree temperature rating, so the specification states 100 degrees. But the equipment may have been designed for, and able to handle, 120. Thus, we establish what the equipment is capable of, and determine its true operating envelope.

Let’s look at this in practice.

The brief

In March this year we completed a study for Repsol in Norway – they’d been working on decommissioning plans for some time and enquired about what subsea reuse entails.

Repsol told us they planned to stop production in a few years’ time and to then start offshore recovery. They asked us to assess what can be reused of their subsea system.

What we did

Our first steps included carrying out a technical assessment of the equipment and gaining a general understanding of its capability. All to estimate the probability of being able to make reuse happen.

We received just short of 230 documents for review. The design data. Install and operating history. Maintenance and upkeep. Residual life estimates.

As the field has operated cyclically, it has not cumulatively produced for very long –only five to six years. So, while it sat on the seabed for the best part of 15 years, it’s seen limited production and the wear and tear was assessed as minimal. It was clear that this equipment had plenty of residual life left.

From here, we proceeded to identify known technical issues and potential modifications to address these, to plan for preservation works and consider potential future reuse scenarios. We then wrapped all this up in a clear set of actionable recommendations for the operator, creating a step-by-step pathway to reuse.


One of the things we confirmed in these studies was that many of the core components were of a high standard in terms of their operating envelope. With that in mind, we went on to identify other areas where the operating envelope may be pushed even further, beyond the original technical specification, increasing the chances of successful reuse.

The results of our study with Repsol included:

  • Outlining what a reuse scenario could look like,
  • Listing actions for the operator – things to be clarified with the original equipment manufacturer,
  • Documenting known issues – items that need to be addressed before assets can be reused,
  • Identifying opportunities where the design may have a bigger operating window,
  • Exploring potential modifications that again may give a bigger field of application.

Repsol told us that when they kicked this study off, they weren’t sure what to expect. But in receiving the report and our findings, they were assured by the thorough approach. We’re looking forward to the next phase of work: collaborating with the original equipment manufacturer and progressing to tender options that include recovery for reuse.

Between this study for Repsol and others, we’re witnessing a turning point. More and more, energy operators are being asked to consider the triangle of reuse, repurpose or waste – it’s in the legislation and increasingly, it’s what societies now expect. And operators are responding – because it makes sense and because it’s the right thing to do.

Before you write anything off, ask yourself if you’re really doing everything you can to make reuse possible. And, when in doubt, talk to a specialist about a feasibility assessment to support your decision making.

For a little investment of time and effort, you may be surprised to find that reuse is more achievable than you first thought, setting you up to recover a portion of your asset’s value and use circularity to reduce landfill and carbon emissions.