This paper presented the design and analysis of a composite production riser (CPR) for a TLP moored by composite tendons in 10,000ft water depth in Gulf of Mexico (GOM). First, a 10 ½" nominal OD composite riser system is selected. The CPR consists of composite riser joints, steel standard and specialty joints. Second, top tension payloads of the CPRs are developed and compared to those of a similar steel riser system. Third, different tensioning options, including conventional hydro pneumatic tensioner, passive spring tensioner, and direct tiedown tensioner are studied. Forth, preliminary riser global analysis, including interference, strength, fatigue, and VIV is carried out to ensure the integrity of the riser system. Last, conclusions and recommendations are made for the studied system. The design and analysis are based on API RP 2RD and DNV RP F202. It is concluded that CPR is a feasible solution for ultra deepwater applications. It is also concluded that direct tiedown tensioner is a feasible solution for TLP top tensioned riser (TTR) in ultra deepwater.
The effort of commercialization of composite material applications in the oil and gas industry has started since a decade ago [15], and has been intensified during recent years in response of the need of the life cycle cost reduction for the ultra deepwater development. The economic advantages were demonstrated on floaters such as TLPs [4, 7], and Spars [9]. From the various possible applications of composite material, composite risers received particular attentions from all aspects, including vendors/manufacturers, operators, engineering services, and regulatory services. Composite riser joint specimens have been manufactured, tested and qualified by different manufacturers [3, 6, 10, 11]. The first composite riser joint was successfully installed in field on Heidrun TLP in 2002 [5]. Composite riser design standard and recommended practice were also published in 2003 by DNV [1, 2]. The comparative risk analysis of the composite riser system is sponsored by MMS (project No. 490) and being carried out by OTRC. It is generally accepted that the top tensioned composite riser system is technically mature [6]. This paper is to further demonstrate the feasibility of the composite riser application from riser global design point of view, which includes riser system general arrangement, tensioning system, strength and fatigue design, and composite riser joint design loads. It has been recognized that composite riser joint, even manufactured by the most up-to-date technology, costs 30% more than its steel counterpart [5]. But possible elimination of external thermal insulation and top tension payload reduction could result in overall cost saving. In some of the previous studies, the riser top tension payloads were estimated without considering the presence of tubing and internal contents. As a result, the presented top tension could be overly optimistic. It is imperative that a practical composite riser system to be designed to confirm the riser top tension payload saving, and quantify the economic value of using composite risers. A TLP has been chosen as the host platform in this study.
