SLWR Innovative Design Methodology Supporting Concept Engineering Through to Project Cost Optimisation

Steel Lazy Wave Risers are one of the most efficient and compliant riser systems for deep-water projects. From a design perspective, designers have to deal with parameters such as the configuration itself, interaction with the FPSO, environmental loads, installation vessel capabilities and commercial issues like installation and procurement costs. This paper presents how to assess the need for Steel Lazy Wave Risers (as opposed to conventional Steel Catenary Risers) and how to develop a state of the art design by using an innovative methodology based on the efficiency of an optimisation through modern technology computation. The objective of the optimisation is to propose a riser configuration that allows the best compromise between all parameters, while remaining fit for purpose and cost-efficient. A methodology was developed using a Python script as an interface between Orcaflex software and the user-defined parameters to best respect the project specific weighted criteria. It will also highlight how the methodology can be applied for fast track conceptual studies, enabling the end user to account for optimised design at the start-up of a field development. All the constraints and objectives will be considered with possible challenges and solutions to be presented. The final design of a lazy waver riser is a compromise between all constraints. This paper provides comprehensive information relative to all the stages of steel lazy wave riser design, from the initial draft configuration to the most optimised and cost-efficient one. A few optimisation possibilities achieved thanks to this process will be developed and illustrated through examples. The concept can be applied to early stage engineering or during the course of a project.