High-performance polymers for oil and gas

Materials World magazine
,
2 Mar 2016

High-performance polymers are finding a range of new applications in the oil and gas sector, with a new generation of high-grade polyamides and polyaryletherketones offering different solutions for an industry traditionally wedded to metal parts. Beth Seares explains.

The advantages of metals such as steel are well known, as are their drawbacks. Several of these, such as susceptibility to corrosion, are highlighted in the harsh operating and environmental conditions found in pipelines and onshore and offshore petrochemicals facilities. In researching a recent report Smithers Rapra has identified new opportunities for improved plastics to rival and surpass metal in several key applications.

The availability of new high-performance polymers is aligning with several longer term trends within the petrochemical sector. First, an interest in prolonging the life of existing assets, as well as an impetus to minimise downtime and stoppages, as well as cutting maintenance cycles, is making an even stronger economic case for more resilient components. Second, the challenges posed by new deposits – especially deeper offshore drilling – and extraction techniques, such as floating and sub-sea production, where plastics can offer a compelling solution. 

The report estimates global demand for high performance polymers in oil and gas applications in 2015 was 17,340 tonnes, with a material value of US$430 million. Growth has been steady in recent years. While global oil and gas production grew by around 1.5% per annum from 2010-14, the use of high performance polymers increased by 4.6% per annum, indicating a reasonable – if not spectacular – amount of steel substitution. A marginal decline in the demand is forecast for 2015–2017, with a return to more healthy levels of growth of 5.6% per annum in 2018–2021. 

In 2016, sales are still at niche market levels, meaning that one or two substantial contracts can considerably influence the demand for an individual material. Polyvinylidene fluoride (PVdF) has enjoyed the greatest recent advance, doing especially well in the flexible pipes sector.

Seals in polytetrafluoroethylene (PTFE) and polyetheretherketone (PEEK) have also benefited from the growing technical demands imposed by deeper, more challenging newer reserves. Other product areas to show positive progress have been wire and cable protection – for downhole cables, umbilicals and other applications – and corrosion resistant coatings and linings for pipes, tanks, vessels and pumps.

Extending the lifetime of assets

The polymer industry is trying to increase the lifetime of the assets associated with recovery, production and processing by providing corrosion-resistant materials. Industry estimates suggest that at least 80% of oil and gas industry products are still metallic and that the impetus for change is sluggish, despite the growing awareness of corrosion issues.

A typical polymer used in such applications is ethylene chlorotrifluoroethylene (ECTFE), a semi-crystalline fluoropolymer that can be melt-processed. It has a good range of properties that make it suitable for chemical resistant applications, such as electromechanical cable jacketing and umbilicals. It is resistant to acids – even at high concentrations and elevated temperatures – caustic media, oxidising agents and many solvents. ECTFE can be used across a wide temperature range – from -70°C to 150°C, continuously. It also has the highest resistance to permeation of all the fluoropolymers and this is a highly relevant factor in the extension of the service life of pipes and pipe linings.

An opportunity for polymers

There are vast reserves of energy in deepwater reservoirs and these account for more than 50% of all new discoveries between 2010–2014. As the industry is forced to drill deeper, extremes of operating temperature and pressure – up to 315°C and 3,000 bars – can be encountered. When combined with aggressive elements, such as hydrogen sulphide (H2S) and carbon dioxide (CO2), and completion and intervention fluids, these are causing major corrosion problems to steel pipes and other metallic components. 

Failures along any part of an offshore or onshore system can often lead to a shutdown of production, which is hugely expensive. Furthermore, in extreme cases, leakages can lead to environmental damage and, sometimes, to severe sanctions from governments.

This scenario presents a major opportunity for suppliers of high performance polymers. High performance materials can make a valuable contribution towards addressing the problems of metal corrosion, which are accentuated as environments become more hostile with extremes of temperature and pressure. Most of the materials highlighted in the report have excellent resistance to these corrosive elements and/or a range of mechanical and electrical properties that make them a viable alternative to corrosion-resistant grades of stainless steel in many applications.

Corrosion-resistant linings

In an industry that is schooled in the tradition of steel products, one major contribution that the polymer industry makes is in the area of corrosion-resistant coatings. Steel is vulnerable to both internal and external corrosion and requires regular inspection and treatment with corrosion inhibitors. Alternatively, corrosion-resistant alloys can be specified, but these are often more expensive than lining a carbon steel product with a corrosion-resistant polymer.

Linings are commonly applied to pipes, tanks and vessels to extend their service life and prevent leaks that might be environmentally hazardous. In the case of pipelines, internal coatings not only provide greater protection from attack by aggressive elements, but can also create a smooth bore which ensures the efficiency of the flow is maintained. This in turn helps to reduce pumping costs.

Tanks linings are very specific to the medium being stored. This might be salt water, oil, drilling mud, chemicals, potable water or sewage. The requirements may include resistance to specific chemicals or abrasion.

A variety of polymeric materials are in use for linings, the most common being thermosets such as epoxy and polyurethane. Epoxy resins have a good range of chemical resistance and adhere well to most substrates. Polyethylene and polyamide are also used but are limited in temperature resistance to around 75°C. PE also does not adhere well and so needs multiple coats. It is also vulnerable to penetration by sharp objects.

Several high-performance polymers are used for coatings but only in low market volumes. They offer excellent levels of resistance to aggressive chemicals and can cope with higher temperatures than most bulk lining polymers. 

The oil and gas industry is becoming familiar with the business case for high performance polymers in replacing steel and other metal components – improved uptime, long life times and reduced maintenance cycles.

With the barrel price of Brent crude falling below US$35 at the beginning of 2016, the industry’s short-term focus is on economy and existing assets. As and when the price of oil increases, firms will look to invest in new equipment, particularly for those marginal extraction facilities in areas that pose the greatest performance demands. These will provide a forum for demonstrating the performance advantages of a new generation of high-grade polymer components and linings and help expand their current niche use. This trend is reflected in the Smithers data, with a 5.6% year-on-year increase forecast to begin in 2018.

Applications where high performance polymers are finding a home

Flexible risers

Used only in offshore oil fields, flexible risers are dynamic pipelines conveying the crude oil from the subsea facilities and flowlines to production or storage facilities. Although generally more costly than traditional steel risers, high-performance polymeric risers have excellent chemical resistance, lower maintenance costs and promise a longer service life. 

Seals

The main high performance polymers used for seals are:

PTFE – for flat seals on flanged joints

PEEK

PAEK 

Long life durability, allied to excellent chemical resistance across a broad range of temperatures, make various fluoropolymers a competitive option, especially at the high performance end of the market. PTFE offers the best range of temperature resistance, being suitable for cryogenic environments at one end of the scale and maintaining performance in continuous service temperatures of up to 260°C at the other. It also offers a very low coefficient of friction and high wear resistance. Furthermore, it can be tailored for each application by using fillers such as carbon fibre, glass fibre, graphite and bronze. These fillers improve properties such as abrasion resistance and mechanical strength, but they can also be used to lower costs.

Wear rings

Wear rings on centrifugal pumps, which are used in many oil refineries, have traditionally been made of metal. These are prone to failure on contact, potentially leading to pump seizure and downtime losses. To avoid this problem, higher clearances need to be designed in. Polymeric alternatives allow for more design flexibility, in terms of clearances, and this factor can enable additional hydraulic force, decreasing vibration and prolonging service life. Wear rings are also a crucial component of impeller assemblies and the polymer industry can add value to these by facilitating tighter clearances. 

Valve seats

A promising application for high-performance thermoplastics is in valve seats. These are usually machined from billets using high-performance polyamides, PTFE or PEEK. Generically, these materials all offer excellent resistance to corrosion, wear and abrasion, low moisture absorption and good dimensional stability, affording greater service life and cost in use. The choice between materials usually depends upon specific circumstances and relative cost. 

Bearings

The function of a bearing is to regulate motion and reduce friction between moving parts within a machine, aiding its efficient operation. Bearings are an essential part of many pieces of machinery used throughout the extraction, storage and refining processes. The  smooth and efficient operation of innumerable pumps, compressors and motors is made possible with the support of bearings. 

The rubbing surfaces of metal bearings are generally lubricated to reduce friction and balls or rollers are widely used to minimise rubbing. However, bearings are always subject to friction and heat build-up, as well as mechanical load. Consequently, they wear out and their failure can result in costly downtime. High-performance polymers offer the prospect of longer service life, even in extreme conditions, and can be a cost-effective alternative to metals when total lifetime costs are taken into account. PTFE is a material with a very low coefficient of friction and is now in fairly common use as a bearing material.

To read more of Smithers Rapra’s report, The Future of High-Performance Polymers for Oil and Gas Markets to 2020, visit bit.ly/1Sdlt5C

Beth Seares is Market Report Commissioning Editor at Smithers Rapra. She has a background in primary and secondary research, with experience as a market analyst and report author. She is currently active in commissioning reports and market forecast data for a variety of raw material segments, including polymers, elastomers, and nonwovens.