Single Independent Riser (SIR) For Future Ultra Deep Water Field Developments

The Single Hybrid Riser (SHR) is considered as a field proven riser solution for deep water field developments and has already been implemented on various projects especially in West of Africa. This paper presents an innovative riser solution called Single Independent Riser (SIR) that addresses key SHR drawbacks and that anticipates the requirements of future challenging field developments. The basic SIR is a balanced cost-risk hybrid riser solution consisting of both a rigid line and a flexible jumper which is vertically tensioned by means of distributed buoyancies along the riser. The major technical advantages of this different design approach with respect to SHR concerns the improved installability by J-lay, improved layout for increased number of risers and the improved dynamic behavior of the rigid riser section under fatigue/extreme environmental conditions. The configuration of the flexible jumper ensures the displacements of the rigid riser section of SIR are significantly decreased compared to SHR. The riser tensioning is achieved using well know high performance syntactic foams that are installed on the SIR rigid riser section using distributed buoyancy coating or discrete buoyancy modules. The syntactic foam can also act as an insulation material for the riser as required. The SIR can be installed using classical J-lay methods and the laying rate is not significantly impacted by the additional distributed buoyancy systems. The riser base can be configured as per the field proven SHR or alternatively based on the much reduced displacements of the rigid bottom section of SIR some further evolutions are envisaged to the basic SIR to eliminate the need for dedicated mechanical articulation (SIR+) and/or flowline PLET/bottom jumper (SIRT). The paper presents the main features of this novel riser technology describing the key results of recent design activities carried out on typical South Atlantic and GOM applications. In addition, an overview of the integrated approach used to develop the SIR concept including design, procurement, fabrication and installation considerations with demonstrable cost-risk balance is presented. Eventually the paper deals with the future evolutions of the SIR solutions and addresses the envisaged qualification program plan