coatings for offshore application

World PiPelines APRIL 2007 www.worldpipelines.com 23

INSULATING SUBSEA PIPELINES

Integrated flow assurance strategies are becoming more critical as the technological complexity of cost-effective oil and gas recovery becomes ever more demanding. Step-out and tie-back lengths continue to increase and maintain a reliable flow of hydrocarbon fluid to the processing facility, which has become a major challenge. The past 10 years has seen

the advent of many chemical strategies for dispersing waxes and inhibiting hydrate formation, and the use of these have become an invaluable part of modern operations. Indeed the use of electrically heated systems1,2 has also become relatively commonplace.

One common factor within all flow assurance strategies is the management of the energy of the system: waxes in general are less likely to precipitate at higher temperatures; hydrates form on cooling at pressure, etc. Thermal management has long been respected as being a field of its own within downstream petrochemical processing, and this is increasingly the case for the upstream oil and gas recovery sector. Being able to control the loss of energy to the surroundings during steady state operation, or to be able to predict the availability of stored energy during periods of operational fluctuation, is an important precursor to being able to design and dimension a reliable flow assurance philosophy for any field.

Passive external insulation, augmented where necessary with electrical heating (electrical resistance, trace, induction) allows for a means of providing a safe base level of performance for flowline and riser systems along with subsea architec-ture. Such systems allow operational flexibility at an affordable cost.

Figure 1. Thermotite® is a five or seven layer thermal insulation coating that is highly engineered and designed to meet aggressive

conditions.

Adam Jackson, Scott James

and Sean Haberer,

Bredero Shaw, introduce

fl ow assurance solutions for

deepwater pipelines.

Figure 1. Thermotite® is a five or seven layer thermal insulation coating that is highly engineered and designed to meet aggressive

conditions.

deepwater pipelines.

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coatings for offshore application

24 World PiPelines APRIL 2007 www.worldpipelines.com

Thermal insulation solutionsHistorically, thermal insulation has been considered during the latter stages of a project, however, increasingly the availability of suitable systems becomes a major driver or limitation in the development of an oil and gas field. The choice of system has indeed been the fundamental dimen-sioning factor in several cases.

When dimensioning a thermal management system, it is essential that all operational and deployment aspects be considered for all elements along the flow conduit. Failure to do so may lead to an under-performing system with seri-ous operational implications for the field as a whole: one typical disjoint of this type being the separate lives that flowlines and risers often live in projects, divorced from manifolds, trees, jumpers, etc.

Bredero Shaw offers flow assurance systems based on thermal management for the offshore oil and gas industry. Its approach is to work together with clients in the develop-ment of tailored systems, where the project requirements are addressed and the latest knowledge and technology within its product portfolio is brought to bear.

Techniques and tools have been developed to enable true end-of-life concept development of insulation systems. Now what does that mean exactly? It means that all insu-lation systems are tested extensively with a view to the changes, either chemical or physical, that the insulant may undergo during the life of an oil and gas field, and these changes are well understood. Furthermore, this means that these parameters, along with their dependence on temperature and pressure, are accurately modelled using verified proprietary tools such that the steady and transient state performance of the system is known at any point in time during the life of the field.

All products are also rigorously tested on a large scale, using specific tests to reveal the system performance during bending, fatigue, shear, trawl and dropped object impact, roller and tensioner loads and simulated service. Many of these tests are so crucial that company invest-ment in equipment is important to secure access and ensure timely completion.

Bredero Shaw is keen to ensure that the best available

knowledge is available to its customers. For example, the company has pioneered the development of high accuracy measurements of thermal conductivity3 and triaxial com-pression and creep testing4 so that the oil and gas industry is better served.

Polypropylene thermal insulation systemsBredero Shaw’s polypropylene solutions include solid, foamed and syntactic materials. Polypropylene is a tough and resilient material that offers several advantages when used for thermal insulation. Polypropylene is a hydrophobic material and does not readily absorb water. The system is immune to hydrolysis, having no labile chemical groupings. This has led to it being accepted for use at temperatures in excess of 140 ˚C. Foaming and application technology, combined with concept development tools, allows for the development of highly efficient cost-effective solutions where requirements arising from several design aspects are married together into a single final multi-component composite product. These products have been successfully deployed using reel, S-lay and J-lay for operation tempera-tures as high as 150 ˚C 5 and water depths as high as 2200 m 6.

Two key aspects are important in system performance,: thermal conductivity (k-value) and heat capacity (Cp). The unique Thermotite® TDF product, developed in-house in Norway, is a high compressive strength, low creep foam, which leverages the naturally high Cp typical for polypro-pylene materials and through low achievable densities, a low k-value.

For applications down to 3200 m water depth, syntactic polypropylene insulation coatings can be applied, where hollow glass microspheres, which reduce the density and therefore the k-value, are dispersed in a mechanically resil-ient polypropylene matrix.

In many cases, the specific field requirements require specific material combinations for optimum solution design. The Thermotite® family of systems are multi-layer compos-ites in which syntactic foams, solid materials and blown foams are combined in unique combinations and applied onto a fully tested 3-layer polypropylene corrosion barrier.

Bredero Shaw has the capability to coat pipe with polypropylene systems at various thicknesses from loca-tions throughout the globe. A recent investment in this technology in Belo Horizonte, Brazil, has resulted in the award of a contract for Petrobras’ PDEG project. Syntactic polypropylene and Thermotite TDF are available in regions of the world where new oil wells are being discovered in very deepwater, such as the Gulf of Mexico and the North Sea.

Polyurethane thermal insulation systemsBredero Shaw offers polyurethane products based on solids and syntactic foams. Shallow water syntactics (ThermoFlo®-S) is based on polymeric microspheres for low k-value. For deeper water applications, however, these are replaced with glass microspheres (ThermoFlo®-D). All systems are based on thoroughly tested (>10 years) poly-ether polyurethane systems. These offer the highest level of hydrothermal stability in the market. Combining this with the extensive mechanical and hydrothermal testing per-formed on these systems renders them one of the most documented systems available.

Figure 2. The Thermotite® family of systems are multi-layer composites.

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Polyurethane systems are applied to the pipe in a molding process, which, along with the rapid cure of the material, leads to high production speed and a close adher-ence to tolerances. The materials are elastomeric by nature, rendering them well suited for deployment using all known techniques. Given their high impact tolerance, moderate k-value and excellent hydrostatic response, these materials are well suited for use in flowline and riser systems.

Extensive internal testing has led to the development of comprehensive design guidelines for the use of such materials.

Future technologyBredero Shaw is committed to leading the market in tech-nology. Four centres of excellence have been established: Toronto (Corporate R&D); Calgary (Technology Services); Norway (Thermoplastic Products); and Ellon (Thermoset products) in order to maintain focus, and to ensure that the future challenges in the oil and gas industry are met with innovative value-added products.

A recent investment in fully instrumented pilot line facilities in Orkanger, Norway, is evidence of this com-mitment.

NotesBP King pipe-in-pipe system (GoM), where hot water is circulated within the annulus between an insulated outer carrier and the inner flow conduit.Statoil Åsgard, Kristin, Huldra and Tyrihans (North Sea).Presented at DOT Houston 2006.Enshrined in the InSpec RP document for thermal insulation coatings.Statoil Kristin.BP Thunder Horse.

1.

2.3.4.5.6.

Insulated pipe destined for the Callanish Brodgar Project in the North Sea.

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