How marine growth is affecting ageing structures in the oil and gas industry

Posted by Andy Norman on 19-Oct-2017 11:00:00

How marine growth is affecting ageing structures in the oil and gas industry

Any structure submerged in the sea will eventually host a community of marine organisms, making biofouling and marine growth an unavoidable issue within the offshore oil and gas industry.  

As previously discussed in the Claxton blog, 50% of all technical integrity incidents are related to ageing assets, so it’s important to slow down this ageing process by introducing preventive measures. Marine growth in particular has huge consequences for structural integrity, hydrodynamic efficiency, and survivability of assets, and these measures can mitigate some of the costs that are amplified by the effects of biofouling.

Read on to find out the effects of biofouling, the issues it can cause, and the plans we can build on to help prevent asset degradation.

What is biofouling?

When oil and gas structures are submerged, they are colonised by, according to Marine paints: The particular case of antifouling paints by Elisabete Almeida, over 1700 species comprising over 4000 organisms responsible for biofouling. These organisms form a community of hard fouling organisms (barnacles, molluscs, and zebra mussels among others) and soft fouling organisms (including seaweed, algae, and biofilm ‘slime’).

The ideal environment for the growth of these organisms starts with bacterial biofilms, which create microenvironments on the structure that are more favourable for the biofouling species. Biofilm cells (or sessile cells) are notoriously difficult to kill, because dense biofilms are barriers that slow down the penetration of biocides found in anti-fouling solutions.

Understanding the cause of, and various challenges posed by biofouling is the first step towards effective biofouling management.

Small but harmful

The development of marine growth’s colonising organisms can lead to the rapid decline of asset integrity. In the case of metallic materials, undesirable changes in material properties due to biofilm are referred to as biocorrosion. Biocorrosion results in billions of dollars in damages each year in the United States alone, and the growth of marine life will eventually lead to visible cracks and dents within assets, resulting in inefficiencies for operators.

The challenges of marine growth

Not only does marine growth thickness affect dimensional measurements of ageing structures, but it can cause handling issues when replacing existing parts due to additional weight. For example, in The Offshore Renewable Energy Catapult’s Marine Growth Mapping and Monitoring, wave energy devices located on the Irish west coast had an increased structural mass of over 10% thanks to marine growth.

Then, when these aged assets face decommissioning, contractors have to combat with constraints in managing the disposal of the assets that have marine growth. According to Oil and Gas UK’s report The Management of Marine Growth During Decommissioning, finding landfill facilities that are sufficiently close and are willing to accept marine growth is a huge challenge for decommissioning contractors. On the evidence of interviews within the report, none of the UK contractors were able to compost their marine growth.

Preventions, precautions and alternatives

Although it’s impossible to completely thwart the natural causes of biofouling, there are preventive measures and efforts that can be taken to preserve asset integrity:

In-water cleaning and preventive chemicals

In-water cleaning can be carried out during Remotely Operated Vehicle (ROV) inspections, with an onboard cleaning kit that enables you to clear away marine growth and corrosion scale. This can be achieved with high pressure jets, but for large areas and equipment, can be time consuming and costly.

Sodium hypochlorite is a simple solution that has been effectively used in the oil and gas industry for years, and is perhaps the most efficient and viable solution to the industry’s biofouling woes. The process only requires three essential ingredients - water, salt and electricity.

Antifouling coatings

Antifouling technology can reduce the detriments of marine growth, including coating and paint that are effective for both offshore oil and gas rigs and ships. The application of such coatings improves the durability and overall performance of assets, with the coating acting as a barrier against corrosion that will degrade and weaken the metal.

High demand for antifouling coatings from the shipping industry is expected to drive the growth of the market in the near future, claims a report by Markets and Markets, which projects the market to grow from $5.61 billion in 2015 to $9.22 billion by 2021.

Accurate risk assessments

As previously covered in the Claxton blog, strong risk-assessment measures can save you money in the long run when dealing with all the elements that relate to ageing assets - and the multitude of issues that cause them, enabling inspectors to spot the health and safety risks and costs caused by biofouling before they become a larger issue.

Rig to Reef - an alternative to removing and preventing marine growth

Rig-to-reef (RTR) is the practice of converting decommissioned platform infrastructure into artificial reefs for the seabed, and is a strong alternative when decommissioning a rig to support a great diversity of marine life. The pros appear to outweigh the cons of choosing RTR when decommissioning a rig, which prove to be popular with sea life over their 20-30 year life span. The legislation of the region will be the deciding factor as to whether a rig can be converted into a reef. In California, offshore companies could be required to fund a state-mandated rigs-to-reefs program, showing a growing trend within the industry.

How Claxton can help

Biofouling is inevitable - but at Claxton, we have a number of solutions to extend the lifetime of your ageing assets anywhere in the world, with our bases in the UK, Norway, and the UAE.

From slot recovery to retrofitting centralizers, find out how we can help assess, prepare and install products into your existing platforms to extend the life of your assets.

Download our free asset life extension buyer's guide to learn more today.

Download the Asset Life Extension Case Study Pack

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