The First Offshore Field Installation for a Composite Riser Joint

Abstract

Abstract 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.