A Novel Free-Standing Riser Concept for Deepwater Developments

Abstract

Free-standing hybrid risers (FSHR) are well established in deepwater field developments in the oil & gas industry. The major advantages foreseen for the FSHR are the possibility of safely anticipating production and requiring significantly reduced payloads at the Floating Production Unit (FPU). This work addresses the feasibility of a novel proposed optimized concept, the Free-Standing Integrated Riser (FSIR), where the pipeline is integrated to the riser by means of a transition section, which is kept in place by a multiple line mooring system, developed to keep the functionality and integrity of the entire riser along its lifetime. The work provides the findings from numerical analysis simulated in Orcaflex, a finite element simulation software dedicated to global analysis of risers, considering the design criteria provided in API 2RD Standard. As part of the FSIR evaluation, screening static analysis was performed to identify the most promising configurations for the multiple line mooring system, followed by a series of dynamic analyses to evaluate the behavior of the riser in extreme conditions. In addition, several investigations were performed to assess the functionality and the robustness of the system, including parametric studies to check for installation and dimensional tolerances, assessment of fatigue damage, and checking the impact of pipe size on the design. The results show that proposed novel FSIR concept can provide a practical and economical solution for deepwater projects.