Stretching the Technology

Published March 20th, 2001 - 02:00 GMT

At it’s production facilities in Moss, Kværner Oilfield Production is rolling out kilometres of new innovations. 

As the focus in oil production stretches further into the abyss, the technology has to follow.  

 

The people at Kværner Oilfield Products (KOP) are doing their part. By making use of technology well-known from KOP’s umbilical production, they have developed the CompTetherTM and the Integrated Production Umbilical (IPU). 

 

Composite Co-operation: 

The CompTetherTM has got it’s name from the composite material it is made of. A 150m CompTetherTM prototype has been manufactured and is now in the process of being tested. 

 

‘We are now doing the final qualification, and we will have a product ready for the market in September 2001,’ says Project Manager for Composite Tethers at KOP, Turid Storhaug. 

 

‘CompTetherTM is both cost-saving and weight-saving compared to traditional steel tethers’, she points out.  

 

Another major advantage of the CompTetherTM is that it can be put to use at much greater depth than its steel counterparts.  

 

At the moment various steel products can usually go to approximately 1000m, and some can be used as deep as 2000m. However, the CompTetherTM is designed to be used at waters as deep as 3,000m. 

 

DNV has been involved in the project through the whole process, by setting standards and testing components. DNV will soon be publishing design guidelines for offshore use of composite materials, to which the CompTetherTM will be qualified. 

 

The Material: 

‘To put it simply, the beauty of composites is that you merge two different materials thereby achieving a new material with the best qualities from both’, Turid Storhaug explains with enthusiasm.  

 

Carbon fibre composite, the material used in CompTetherTM, has been extensively tested, showing reassuring results. One stick of it, about as thick as undersigned’s pencils, is said to be able to carry three large cars. In the prototype CompTetherTM there are 781 such sticks.  

 

The number of sticks and their thickness can be altered. Fiberoptic cables can also be added, to monitor the tether. This is all assembled together with PVC profiles and coated in polyethylene, on reels at KOP’s production facilities at Moss, south of Oslo.  

 

By altering the composite ‘formula’ its qualities can be changed to suit different needs with regard to criterias such as stiffness, strength, corrosion resistance etc.  

 

‘There has been a tremendous growth in the use of carbon fibre composite materials over the past 30 years’, says Storhaug. ‘The price of the material has dropped accordingly’, she adds. 

 

30 years ago carbon fibre composites were mainly put to use in sky-rocketing aerospace projects. The cost was accordingly high. Today it is used for sporting equipment, parachutes and bridges, among other things.  

 

It is also expected to be used to a much larger degree within the automobile, infrastrucure and marine industry in the years ahead. That will give a significant rise in material output, and correspondingly lower prices. 

 

‘According to our study, even today’s prices will give a cost-reduction with the CompTetherTM at 800m depth. The cost saving will increase as it is used in even deeper waters, in addition to the fact that steel products are not available beyond 2,000m depth’, says Storhaug. 

 

The CompTetherTM is supposed to reduce both Capex and Opex, as it has a broader versatility than it’s steel counterparts, and it requires considerably less maintenance.  

 

It is also easier, less expensive and safer to install than earlier types. The installation process is similar to umbilicals. It is rolled up on ~4.5m diameter reels and shipped out. Out on the field it is easily unreeled straight into position.  

 

‘Installation of conventional tethers is often done by dragging it out to sea. Conoco has lost several tethers that way,’ Storhaug says. 

 

Versatility: 

The CompTetherTM is first of all designed for mooring of TLP-platforms. It can also be put to further use, such as mooring of subsea tunnels and pipes. 

 

As the end is near for many ‘old fields’ there is a growing need for technology which enables re-use of platforms and equipment. By using the CompTetherTM it will be possible to move an existing floater to extended water depths.  

 

Many floaters designed for shallow waters can be employed at water depths down to 3,000m, making them attractive within new fields in the Gulf of Mexico and West of Africa. 

 

Conoco has several old platforms which, with CompTetherTM, it will be possible to move to deeper waters. The first projects are likely to be on 1,500m depth. But by September 2001, the CompTetherTM will be qualified for use as deep as 3,000m, Storhaug promises. 

 

Subsea Infrastructure: 

‘KOP has a goal of becoming world leader on subsea infrastructure’, says Technical Manager for Umbilical Systems, Ole Heggdal. The company is already a major player within umbilicals.  

 

Now they have developed the steel tube technology further, creating the Integrated Production Umilical (IPU). This is a step further from the integrated service umbilical with 2-3” centerline that Kværner has developed and successfully implemented during the past decade.  

 

The IPU can have a large bore central pipe, 6”-12”, suitable to transport well fluid, water, gas or any other fluid that are required in large quantities.  

 

The IPU is intended for subsea tieback of one or several subsea wells in one single continuous length from 10-15 km, but larger distances have also been studied. 

 

The IPU is an all-in-one product and around the central line, an annular shaped thermal insulation matrix comprising umbilical lines with signal and power cables, thermal monitoring as well as a heating system.  

 

This means both CAPEX and OPEX reductions by reduced installation, subsea flow-line and umbilical infrastructure and continues injection of hydrate inhibitors.  

 

Avoids Hydrate: 

It also assures cost effective operation through its flow assurance. The definition of flow assurance is the ability to produce and transport multiphase fluids from reservoirs to processing plants in a cost-effective manner. 

 

A main obstacle to flow assurance is hydrate plugging and wax deposition in pipelines. Conventional methods for minimising hydrate and wax problems, such as injection of hydrate inhibitor, have several disadvantages.  

 

They can be costly, require large storage and contaminate both oil and water. On the other hand, the problems can be avoided by using the IPU concept as a control method.  

 

The combination of an insulated and heated pipeline makes it possible to avoid hydrate and wax deposition. Should the problem still arise, will the heating system be able to monitor temperature along the flowline and give a defined amount of heat into the pipeline at any point in order to melt hydrates. 

 

‘In the coming years it will be technically and commercially more attractive to invest in environmentally friendly subsea hydrocarbon production systems, especially systems that avoids extensive use of costly chemicals’, says Heggdal. 

 

Proven Technology: 

‘The IPU is a further development from earlier field-proven umbilical technology from KOP. It also has a lot in common with the free-hanging metallic risers, which is considered established technology.’ says Heggdal.  

 

The IPU can be laid continuously from the platform deck to the subsea well without joints. And it will fit both shallow and deep water, static and dynamic applications.  

 

‘It can also be designed to fit specific needs’ i.e. gas lift or continues heating by means of produced water. The heating is either a hot water system or an electrical heat tracing system. According to Heggdal this is also an improved concept, with high reliability and efficiency. 

 

Installation of the IPU should be as easy as an umbilical. It is produced onto large reels, and can be launched from conventional laying vessels. The IPU can be fabricated in Moss onto carousels with capacity 2000 to 3000 tone, that can take 15 km IPU. 

 

The final stage of the development of the IPU has been a joint industry project between KOP, Statoil and ExxonMobil. The remaining qualification work includes testing of a 10” IPU for static and dynamic applications.  

 

Many oil companies are at the moment evaluating the IPU for possible projects. The IPU will be commercially available during the summer 2001.  

By: Åse P. Thirud 

(scandoil

 

© 2001 Mena Report (www.menareport.com)

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