The Single Hybrid Riser (SHR) concept has been used successfully in industry on floaters such as Floating Production, Storage and Offloading (FPSO) vessels in deepwater applications. This concept is especially effective with floaters in areas where challenging metocean environments result in severe vessel motions. The flexible jumper connecting the vessel to the rigid steel riser effectively isolates the dynamic vessel motions from the top-tensioned steel riser section. This results in lower strength and fatigue demand in the steel pipe section as compared to other riser concepts such as a Steel Catenary Riser (SCR). However, the SHR concept also reaches the design limits of the flexible jumper as pressure, temperature, and sour service operating conditions become more severe.
ExxonMobil has demonstrated the feasibility of using a Steel Catenary Jumper (SCJ) as an alternative to the flexible jumper for extending the operational limits of the SHR concept. This paper presents the results and design considerations for a SHR with a SCJ in 10,000 ft. Water Depth (WD) and pressures up to 10 ksi. The SHR/SCJ configuration was determined iteratively by assessing its strength performance in response to wave and current loading, vessel offset, internal content and pressure. Satisfactory strength and fatigue performance is achieved under harsh North Atlantic and West Africa environments with a predominant fatigue condition. As is the case for SHRs with flexible jumpers in similar conditions, vessel heading control is required to maintain acceptable response during extreme and long term environmental loading. Installation of the SHR/SCJ concept is determined to be within the present market capability of heavy lift vessels, new generation J-lay vessels and FPSO pull-in facilities. A fabrication and installation procedure for the SHR/SCJ configuration is presented.
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