The global annual expenditure to mitigate corrosion is in the range of $2.5 trillion, roughly equal to 3.4% of the world’s GDP, according to NAC International. The corrosion problem is further magnified by enhanced oil recovery rates from mature fields. The use of water injection methods for example, is leading hydrocarbons to become sourer, thereby over time, the production fluid that flows through the pipeline gradually becomes more corrosive. This is an increasingly complex challenge for operators around the globe as they are looking to raise production and profits while countering the potentially catastrophic consequences of corrosion with relatively ineffective and expensive inhibitors.
Until a decade ago, steel material for pipelines and pipe structures was the main option for the oil and gas industry. Now, Strohm is leading the development and deployment of Thermoplastic Composite Pipe (TCP) to counter the inherent drawbacks of steel: corrosion, fatigue and weight.
There is now a growing variety of applications offshore which include flowlines, risers, jumpers and lines for uses such as chemical injection, methanol injection, gas lift, decommissioning and intervention.
“Often, systems used to mitigate corrosion through pumping corrosion inhibitors need to have an up time above 90% to be effective. Depending on the region, that is rarely achieved. For instance in Asia, operators are sometimes at only 50% up time on their corrosion inhibitor system and find it very difficult to increase this uptime , as it requires a constant supply of chemicals to the various platforms, working pumps and available power supply, all of which are working in a harsh offshore environment. Typically, for every month they lose on corrosion inhibitors, they lose a whole year of design life of the pipeline” explained Martin van Onna, chief commercial officer with Strohm.
The composite pipe dream comes true
TCP features a solid pipe wall constructed from glass or carbon reinforcement fibres and thermoplastic polymeric materials. The unique and proprietary melt-fusing manufacturing process results in a true composite structure, with the fibres fully embedded within the polymer matrix and ensuring the strongest interface possible between the different pipe layers. The fibres are linear in behaviour and typically do not show plastic deformation or yielding. This creates a robust spoolable pipe, 80% lighter than metallic equivalents, and adapted to customer-specific requirements.
Based on the application, the company selects the right thermoplastic matrix and fibre to ensure it has the best fit-for-purpose solution for highly loaded, critical applications in the challenging offshore and subsea environments.
TCP can be installed with smaller vessels than traditional steel-based pipes. Where required, a weight coating can be applied, again based on the same polymer with additional heavy compounds.
Strohm is fully qualified to DNV GL standards and was instrumental in the creation of the first standard for the requirements for flexible TCP for offshore applications, DNVGL-ST-F119. The document supports operators in their choice of TCP instead of steel or traditional flexibles for pipelines or risers.
The corrosive conundrum
Over the past 10 years there has been a relatively slow uptake in this new material. Residual reticence to adapt and change coupled with general ignorance on the benefits TCP can bring is now dissipating. In today’s cost-conscious climate, eliminating the corrosion problem and the issues it brings, while drastically slashing the cost for subsea infrastructure, are the two primary reasons for operators now assertively switching from steel to composite.
“The value proposition that TCP has is two-fold,” said Van Onna. “One is completely doing away with corrosion and the other is the reduction in total installation costs. This cost element is all around the ability to use small vessels to transport and install our pipes in a very cost-effective manner. This is not possible with steel pipes, because you have to mobilize the pipelay barge, which often has to come from other regions, before you can start installing your pipelines.”
“As TCP Flowline is supplied in long, spoolable lengths, it is particularly cost-effective for horizontal lay methods, using rental reel drive and overboarding systems that can be placed on smaller vessels, resulting in around 40% saving on as-installed cost. In addition, the lack of corrosion reduces associated corrosion-related costs such as pumping of corrosion inhibitors, related pigging, and inspection and maintenance requirements.”
At the time, the operator had a large stock of corroding subsea flowlines suffering from sulphur reducing bacteria, or microbacteria induced corrosion.2 This led to an extensive five-year qualification program which included lab and prototype testing as well as full-scale offshore installation trials. In 2017, Petronas installed the world’s first pilot TCP Flowline in Malaysia for hydrocarbon service. A year later it was awarded Technology Readiness Level (TRL) 6 following comprehensive monitoring of the flowline.
TCP solutions, manufactured up to 7.5” ID, 121oC (250oF) and 10ksi working pressure, for hydrocarbon production, water, gas lift, and chemicals injection have since been installed in West Africa and the North Sea, and current projects will be delivered Australia and West Africa for installation later this year.
The third value proposition: lower CO₂ footprint
“TCP’s main value proposition has focused on the ‘no corrosion’ and ‘lower total installed cost’ elements. While these remain important, we have also recently become aware of a third added value: TCP operations offer a lower CO₂ footprint,” revealed Van Onna.
“With a backdrop of operators targeting a net-zero goal, CO₂ offsetting attracting bad press, and a sharper focus on the the complete chain’s footprint, the lower CO₂ footprint of TCP can play a big role in the successful sustainability efforts of our clients. From a manufacturing point of view, studies have shown that TCP has a much smaller carbon footprint compared to steel pipelines , and its installation provides even bigger savings on CO₂. We are able to provide operators with exact and certified data, thereby enabling them in their efforts.”
Life extension and production optimisation
The company employs a specific ‘staircase approach’ for each of its clients, whereby operators can execute collaborative studies and pilots to optimize the disruptive potential and performance of TCP in their operations as well as build acceptance within the organization. Brownfield applications such water injection and gas lift are ideal first applications for TCP, where the business case is strong and return on investment high.
Some of the latest contract awards include:
- A gas lift jumper for Anasuria Operating Company, to support operations in the Guillemot field, approximately 175km east of Aberdeen (Figure 4).3
- A 4 km flowline for a supermajor in West Africa, for water injection.
- Two off methanol injection jumpers for a large operator in Asia
“We allow the operator to use small vessels that are already in-country. Especially in West Africa, this makes a huge, very powerful case. Small vessels that are already in Angola, or in Ghana or in Nigeria, can be used to install our pipes. So, the mobilization cost is almost totally avoided. Also, you don’t incur transit costs and as our pipes are lightweight, transportation is very easy. All this make it very cost-effective.”
For mature sectors such as the North Sea, TCP is proving its credibility to help enhance production particularly in brownfields for the replacement of old pipelines and/or the installation of gas lift.
“At some point production hits a low level of a couple of thousand barrels. Many of the bigger companies will abandon this and stop production,” Van Onna believes. “However, the firms that specialize in lengthening the field life through our gas lift products for example, are able to add an extra 10, 20 years or more of continuous production from a very low level. That way you can get out much more oil and increase the recovery ratios.”
Innovation in the pipeline
In line with DNVGL-ST-F119, the IJmuiden headquartered business has carried out several qualification programmes to certify its design methodology, production and materials for all its products. “Compared to steel pipe, TCP is competitive on up to 10 to 20 km of pipe. For corrosion resistant alloy, TCP is competitive altogether,” stated Van Onna.
The company is continuing to develop, qualify and deploy new and more advanced TCP products. This includes:
- Carbon fibre with polyamide 12 (PA12), DNV qualified to 10,000 psi (689 bar) and 80oC (180oF) in use for water injection in the Gulf of Mexico
- Carbon fibre with polyvinylidene difluoride (PVDF) is now being qualified for up to 10,000 psi and 121oC (250oF). The combination of fibre and polymer offers the best alliance of submerged weight, chemical resistance, and minimum bend radius and will enable the commercial deployment of TCP dynamic risers (Figure 5)
- Weight coating to give pipes greater stability on the seabed, without having to work with ballast elements or concrete, ropes or chains
- Development of ‘smart pipe’, such as the integration of optical fibers and sensing
- Enhanced insulation for higher temperature applications.
Carbon steel structures exposed to natural waters and corrosive environments generally corrode at an unacceptably high rate unless preventive actions are taken. An estimated one-sixth of all steel production worldwide is used to replace corroded metal, much of it at cooling water piping systems, and yet the rate of corrosion in pipelines is increasing and becoming more difficult to overcome.
Aker Solutions, Shell, Chevron, Evonik, Saudi Aramco, Subsea 7 and Sumitomo Corporation have all demonstrated belief in the future of disruptive composites for oil and gas applications with major investments in the company.
“The corrosion challenge is a massive issue in the industry. Next to fire, pipeline corrosion represents the most serious threat and monetary loss to any commercial or industrial building, or plant operation. In our case, we simply take it out of the equation, which is why TCP is ultimately so disruptive,” concluded Van Onna.
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