The first offshore demonstration of composite risers was successfully conducted on the Heidrun TLP in the Norwegian North Sea during the period from July 2001 to January 2002. The field demonstration involved the installation of a full size high-pressure composite drilling riser joint, and using it to drill three wells while located at different positions along the riser string. This successful demonstration should pave the way for the commercial use of composite risers for deep-water applications. Qualification tests have demonstrated that composite risers can be designed to satisfy all operational, environmental, and regulatory requirements. The success of this field demonstration in establishing confidence in the composite riser technology was confirmed when the Heidrun operator decided, after the completion of the third well, to use the composite riser joint for drilling additional wells. The paper presents the key issues associated with design, fabrication, qualification, certification, interface with operations, and field demonstration of the 15 m long 22" ID composite drilling riser joint. In addition, current plans for further development and commercialization will be highlighted. Introduction A key imperative to deepwater developments is continued technological advances to improve project profitability and enhance operational safety and environmental stewardship. Composite materials provide many desired properties such as high strength to weight ratio, excellent fatigue properties, good corrosion resistance, good thermal insulation, and increased design flexibility that allows achieving this goal for the riser systems. Improvements in project profitability can usually be achieved through reduction in capital cost and/or reduction in operating and maintenance costs. Since the cost of composite riser joints is about 30% higher than equivalent steel riser joints, improvement in project profitability can only be realized by improvements based on system and/or life cycle costs. Composite risers can impact the life cycle economics by improving payload capacity, increasing water depth capability, improving overall system safety and reliability, and reducing maintenance costs. Numerous case studies were performed by both oil companies and engineering contractors that demonstrated the economic value of composite risers for deepwater production and drilling platforms [1-6]. As an example, composite drilling risers require less buoyancy than steel counterparts and allow for more riser joints to be stored on the deck and fitting through a smaller rotary table. Also, the lighter composite riser joints mean less required tension and a smaller deck load, which would allow a rig to carry extra casing. In addition, composite risers have high internal damping that can help in reducing the risk of vortex-induced vibrations. In spite of the high level of interest in composite risers and the large business opportunity, the commercial application of composite risers remains tentative because of uncertainties associated with the difficulty of introducing new technology. This difficulty arises from emotional and perceived technical barriers, in addition to serious concerns regarding potential escalation of cost and delays in schedule. It is believed that these barriers are generally removed after the first use.

A key imperative to deepwater development is continued technological advances to reduce the development cost while improving reliability. Therefore, composite materials are being considered for several water depth sensitive systems such as risers and tethers. This paper focuses on the application of the composites technology that is being developed through the Conoco/Kværner Composite Alliance as part of the effort to promote the commercialisation of composite risers and tethers. The paper demonstrates the economic impact and the enabling capability of composite tethers and risers for ultra deepwater TLP's. Benchmark cost of conventional TLP solutions with TLP solutions based on composite tethers and risers is being presented. Subjects to be covered in details are:Feasibility of composite tethers and risers for deep and ultra deep water TLP applications,Composite risers and tethers impact on overall TLP design,Design and fabrication of composite tethers. Also presented, are the results of a composite tether prototype development that is being performed as part of a DEMO 2000 project. Introduction For deepwater developments with floating structures, the use of lightweight and high-strength materials has become increasingly important. Increased water depth generally means increased weight and tension from risers and station keeping systems. These effects have to be compensated for with additional buoyancy; which results in increased displacement and dynamic mass of the floating structure. This again requires larger station keeping systems, and the design spiral continues until convergence is achieved. Generally, the use of composites and advanced materials reduces the requirement for increasing the displacement. This effect becomes more important as the water depth increases. The cost benefits gained by introducing composites are dependent on the type of concept and where the substitution takes place. The more weight-sensitive the concept is, the larger the gain will be. The most sensitive floating concepts are the TLP followed by the Semi, and the least sensitive is the FPSO. Through the Conoco/Kværner Composite Alliance, both Kvaerner and Conoco have performed significant work to assess the global impact of the use of composites on overall platform configuration. The costs associated with composite applications, and the cost reduction for the entire system when substituting composites for steel, has also been extensively investigated. The reduction of the system cost is important since the procurement costs for composite components are generally higher than equivalent steel components by a factor of 1.5 to 2.0. Although several studies have shown that the use of composite materials in risers and tethers results in many benefits and that the market potential is large, several hurdles remain before the technology becomes commercially available. One of the main objectives of the Kværner/Conoco Composite Alliance is to overcome these hurdles. The current plan is to complete by the end of 2001 programmes for the demonstration of full scale fabrication and installation of both composite risers (CompRiser?) and composite tether (CompTether?). In addition, systems for certification and quality control will be established according to DNV design guidelines for composites offshore.