The Development of a Free-Standing Integrated Riser

Abstract

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 accelerate production ramp-up and requiring significantly reduced payloads at the Floating Production Unit (FPU). This work addresses the feasibility of an optimized FSHR 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, which is designed to keep the functionality and integrity of the entire riser along its lifetime. The work applies numerical analysis simulated in Orcaflex; a finite element simulation software dedicated to global analysis of risers. As part of the FSIR evaluation, screening static analysis was performed to identify the most promises configurations for the multiple line mooring system, followed by a series of dynamic analyzes 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 how the pipe sizes would impact the design. The work also provides an economic analysis to evaluate how the application of the FSIR can influence the project Net Present Value (NPV) in deepwater fields such as in the Pre-Salt developments. As a result, the FSIR has shown to be a potential solution for deepwater developments, demonstrating significant benefits against the most conventional FSHR, due to its simplicity, eliminating the need for the rigid spool, the flex-joint at the foundation, the Pipe Line End Termination (PLET), the riser lower assembly and the stress joint at the bottom of the riser. In conclusion, the novel riser system should be more economical and safer than the traditional FSHR, being possible to obtain large savings with equipment and installation time, while keeping the same advantages of being decoupled from the FPU motions and allowing for the pre-installation of the subsea system, limiting the installation schedule risk and allowing for an accelerated production ramp-up, when compared to other traditional dynamic riser systems. Overall, this new concept should lead to a considerable increase in the NPV for the projects. It is important to highlight, however, that the availability of the technology still requires the qualification program to be completed, in order to ensure that all potential risks have been properly identified, evaluated and controlled.