Thermoplastic composite solution for deep oil and gas reserves - Part 1

Humanity’s insatiable demand for oil and gas (O&G) is driving the exploitation of offshore reserves that are ever deeper and harder to bring to the surface. This is subjecting the risers, flowlines, tubulars and other pipework used to access and work sub-sea locations to greater loads, pressures and environmental challenges.

At the same time, pipes need to be as light as possible in order to stay within the payload capacity of floating rigs and storage platforms.

Overall, the physical demands are beginning to exceed the affordable capabilities of present technology-based piping that is primarily metal. Reinforced plastics, in particular reinforced thermoplastic composites, could be an answer.

Why thermoplastics?

According to Dr Rod Martin and Dr Morris Roseman from Element Hitchin (MERL) (formerly the Materials Engineering Laboratory Ltd), composites are key to enabling the industry to meet some of the energy security challenges that nations face today. The ability to combine tailored strength with flexibility, low weight, high thermal and pressure tolerance, minimal flow resistance, high resilience and durability in large-bore pipes enables them to surpass the capabilities of current predominantly metal piping – albeit often polymer lined.

Conventional thermoset composites have been tried (for example Compipe, developed in Norway in the late 1990s, comprised reinforced epoxy pipe with an unreinforced thermoplastic liner) are a poor substitute for metals because their cure dynamics are a barrier to the continuous production processes desired for pipe manufacture.

Thermoplastics, on the other hand, lend themselves to continuous flow production since consolidation and cure are not the issue they are with thermosets.

Element Hitchin is part of a consortium that has evaluated the suitability of various thermoplastic composites for flowlines. Glass fibre reinforced polyoxymethylene (POM) and polypropylene (PP) performed well in saltwater, while carbon fibre reinforced polyetheretherketone (PEEK) proved well suited to a sour oil environment. Carbon in polyphenylene sulphide (PPS) behaved well in a sour oil environment and in hydrocarbon gas condensate at elevated temperature. (NB: A sour oil environment is one where oil is mixed with water, a variety of chemicals, reagents, hydrocarbon by-products, sand etc, a number of which can challenge the impermeability and longevity of certain thermoplastics.)

Thermoplastic composites can be manufactured in continuous spoolable lengths using tape placement or filament winding methods and a number of companies are now developing this capability for the primary structure of pipes used in the oil and gas sector.

Airborne International BV in the Netherlands, for example, has implemented what it claims to be the world’s first dedicated manufacturing facility for the continuous production of high-end fully bonded thermoplastic composite tubulars, having last year commissioned two production lines in a 9,000 m² factory in Ijmuiden.

Airborne’s pipe concept features two layers of glass or carbon fibre melt-fused into thermoplastic polymer to form a fully bonded solid-wall pipe. Lighter and more flexible than metal pipe, the product is more easily spooled and transported, and is deployable from smaller vessels than would be required for conventional pipe. The pipes are strong, rugged and have good burst resistance under pressure. They do not corrode and are resistant to a wide range of chemicals and progressive degradation in water. Their smooth bore facilitates flow while other attributes include high thermal tolerance, fatigue resistance and durability.

The fact that the material exhibits ductile rather than brittle behaviour extends service life. Use of the same thermoplastic polymer for the liner, composite layers and outer jacket make for a one-material solution for heavy-duty pipes.

Asserts Martin van Onna, Commercial Director of Airborne Oil and Gas: “Overall, they are the answer for high-pressure, high-temperature risers in the deepest water.”

Airborne’s award-winning technology has scored with Petronas, which has selected it for offshore flowlines and is running a qualification programme with Saipem SA for a 2.5 km downline for the Guara and Lula Northeast gasline project in Brazil.

In the same viccinity, US firm Oceaneering Inc is producing many kilometers of thermoplastic production control umbilical that Petrobras will utilise in harvesting deep reserves in the Espirito Santo Basin. Oceaneering produces hose in bores ranging from 3 in to 16 in diameter suitable for pressures of 3,000-15,000 psi. High collapse resistant (HCR) thermoplastic is available for the injection of low-weight chemicals in deepwater applications.

UK solution

Meanwhile in Portsmouth, UK, Magma Global Ltd is on the verge of commissioning new production capacity, in this case to manufacture pipe that is made from carbon fibre-reinforced PEEK thermoplastic. So far it has been producing lengths of up to 25 m for test and development purposes, but a new production line soon to be commissioned at the Portsmouth factory will start producing continuous lengths for spooling and subsequent deployment at O&G fields.

The company was founded in 2010 by Martin Jones and Damon Roberts, CEO and Engineering Director respectively. They had become exposed to O&G activities while developing sensitive fibre-optic equipment for measuring strain in masts and other structures when working with their previous company, Insensys (subsequently acquired by Schlumberger). The pair had gained knowledge of the load cases experienced in O&G along with awareness that major improvement in pipe technology would be needed for future O&G exploitation. Their composites expertise derived from experience at Insensys with designing and producing advanced composite masts, usually with embedded fibre-optic strain sensing, for high-performance superyachts. This business is still on-going, under the Magma umbrella.

From the start at Magma, they decided that a high-end product based on carbon-PEEK would be the best solution, despite the high costs of both material phases.

As Roberts told Reinforced Plastics: “We noted that there was a clear demand for pipe suitable for deep water, high pressure and sometimes high temperature applications where existing materials were inadequate. Low-cost materials and manufacture were therefore not for us. We needed a high-specification solution that could be manufactured with precision, repeatability and consistency. Carbon-PEEK meets this need while being supremely strong and resilient, and for us it was the best choice.”

PEEK has a Tg of 143°C but retains good structural properties at up to 200°C. Magma typically uses a composite comprising high performance carbon fibre (from Toray, with a tensile strength of 4.9 GPa) in a Victrex PEEK matrix. While high strength, medium modulus carbon is the majority reinforcement, some medium modulus and even high modulus grades are selected for areas where the highest strength and toughness are needed.

Roberts and his team have developed a proprietary manufacturing method able to combine the two material phases and deliver pipe in continuous lengths of up to 2 km plus. The technique is described as automatic, robotic, scalable and monitorable, the continuous process being able to deliver high product quality and consistency. A leading advantage of the method is that all necessary operations take place in a single pass. Pipes of up to 24 inches in internal diameter can be produced.

While conceding that basic material cost is high, Roberts argues that the as deployed cost is increasingly competitive with other technologies, particularly steel-based pipe.

As he points out: “The fact that our pipe is more flexible and spoolable than steel, and is also much lighter, means that it can be carried and deployed from smaller vessels and managed more easily. In water it has about a tenth the weight of steel. Moreover, reliability issues with present technology mean that cost estimates for deploying and commissioning steel pipe are often exceeded. All this affects the relative costs. Moreover, the as-deployed cost is one thing, but if you then consider through-life cost, our winning margin is increased because our material is so resilient and durable.”

Specific pipe products include m-pipe™ and s-pipe™, both of which can be produced in discrete lengths or as continuous spoolable product. Lengths are equipped with end fittings and, where required, a flange or threaded coupling. Available in diameters of 2 inches to 2 ft, m-pipe is suitable for a range of risers, flowlines and umbilicals. Low weight, along with high strength and strain capabilities, facilitate installation.
s-pipe, though materially similar to m-pipe, s-pipe, is targeted at small bore and intervention applications typically up to 3 inches in diameter. Described as ideal for challenging intervention and work-over applications, it can be purchased in 5, 10, 15 and 20 ksi versions. This product was announced at last year’s Offshore Technology Conference (OTC) in Houston, Texas, where it attracted considerable interest. ♦
 

Part 2 of this feature is available here.

This article will also be published in the July/August issue of Reinforced Plastics magazine.

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