EoW March 2010

technical article

Use of high performance elastomers in cables for offshore platforms in Arctic regions Manuel La Rosa and Andreas Roos, Lanxess Deutschland GmbH Technical Rubber Products, Leverkusen, Germany

Abstract Sakhalin Island and the Shtokman gas field in the Barents Sea are among the regions with the most challenging operating environment in the world. Offshore platforms for these regions must meet tough standards, especially regarding cables for control panels and instrumentation. High flexibility at low temperatures (-50°C), outstanding oil resistance, flame retardant and non-corrosive properties are just a few of the requirements. Ethylene vinyl acetate (copolymers) EVM (Levapren ® ) and hydrogenated nitrile butadiene rubber HNBR (Therban ® ) are well suited for meeting these challenges. Their halogen-free character, good oil resistance, ozone and UV light resistance, combined with good mechanical performance in a wide temperature range (–40°C to 175°C) make this material ideal for cables used in offshore platforms in Arctic regions. This paper presents several compounds based on blends of HNBR and EVM, tested according to international standards such as IEEE 1580, NEK 606 and BS 6883. Resistance to aggressive fluids, such as oil and water-based drilling muds, has been tested. Mechanical property performance was tested at –50°C.

Cable standards for oil platforms NEK 606 is the international industry standard for the offshore oil and gas, ship and marine industries. These cables are Det Norske Veritas (DNV) certified to be in accordance with ISO 9001 and 14001. The construction of NEK 606 cables for offshore platforms is similar to other standards such as BS 6883 and IEEE 1580 type P [4] . 1.2 High performance elastomers for cables used in cold climate 1.2.1 Levapren® ethylene vinyl acetate copolymers (EVM) Ethylene vinyl acetate copolymers with a content of 40% to 90% vinyl acetate (VA) are known as rubber-like materials. The saturated backbone of the polymer chain gives EVM excellent ozone and weather resistance. They also exhibit high temperature resistance up to 175°C and the increase of VA content from 40% to 90% allows a significant improvement of the already very good oil resistance [5] . 1.2.2 Therban® hydrogenated nitrile butadiene rubber (HNBR) HNBR is a nearly ideal polymer to deliver the performance criteria required in Arctic environments. Its outstanding property profile is due to the saturated polymer backbone in combination with highly polar and inert ACN side group. All this provides the necessary properties to withstand severe ozone and UV weathering, to maintain flexibility at low temperatures, to resist the attack of highly polar fluids and oils, resist high temperatures (up to 150°C) and maintain mechanical properties performance [6] . The low temperature and oil resistance properties of Therban ® grades are strongly linked to the acrylonitrile (ACN)

making navigation and oil exploration and production possible in the Arctic sea. The challenges of this endeavour are numerous: remote offshore locations, harsh environmental conditions and a fragile geo-political arena. Typical examples of the harsh Arctic environment are the Shtokman and Barents Sea fields ( Figure 1 ). This project anticipates an annual production of 70 billion cubic metres of natural gas and 0.6 million tonnes of gas condensate, comparable to the annual gas output of Norway, one of the largest European gas suppliers [1] . Located 550km offshore, the field cannot be reached by helicopter from continental bases. Freezing winds, very low temperatures and six months of winter darkness add to the challenges of developing this field [2] . To drill in deeper water required ice-strengthened drill ships, including a revolutionary, eight-sided vessel. Other innovations were airstrips built of thickened ice, new icebreaker designs, ice-breaking supply boats, and floating dry-docks for servicing the other ships on site. Without these developments, exploration and production in the Arctic would not be possible [3] .

Figure 1 ▼ ▼ : Platforms operate under extreme conditions in the Arctic

1 Introduction 1.1 The Arctic challenge Oil exploration and production in the Arctic region

Russia, Canada, Norway and the USA are among countries looking to explore and develop hydrocarbon resources in the Arctic region. Melting of the ice cap of the North Pole is anticipated in fifty years,

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EuroWire – March 2010