Learnings from Offshore Oil and Gas: Key Translational Success Factors in Mooring Hookup and Tensioning Methods for Floating Wind

Abstract

Abstract Optimized moorings are essential to floating wind feasibility. The identification of key factors for the choice of mooring connection method is vital for the successful installation of a commercial scale floating offshore wind farm. Commercial scale floating wind farms will require quick connection with minimization of costs, risk, safety hazards and operational time offshore. Furthermore, any delays in the installation of floaters can cause a bottleneck in the industrialized production line as wet storage in the ports are finite. These challenges make choosing the right technology early in the development and planning stages crucial. If the wrong strategy is chosen, offshore installation can become the most expensive part of the project. A simple disconnection method must also be available for the future should there be a need to tow the floating offshore wind platform with turbine back to port for major maintenance. Presenting a case study from a successful mooring hook up and tensioning operation for a recent Floating Production Unit (FPU), we evaluate an optimized strategy for the installation of a typical wind farm. The case study demonstrates quick connection and re-tensioning capabilities. Additionally, the ability to quickly disconnect for towing back to shore is evaluated. Methods to reduce vessel spread requirements, increase weather windows and de-risk offshore operations are demonstrated. Key factors are identified to assist in early-stage decision making which affect aspects of the floater design and installation strategies. Increasing weather windows for mooring installation is critical to operational success. When projects reach storm safe condition expeditiously, costs and risk associated with anchor handlers, tugs, crew, and equipment are minimized. The metocean conditions in many floating wind farm locations pose challenges in the form of wave height and current. The industry must improve operational limitations for these conditions. Choosing a method that reduces time offshore for anchor handling vessels with high day rates reduces project cost and increases schedule flexibility. The hook up and tensioning methodology selected have a direct effect on vessel spread required, project risk, and cost to support mooring operations. For example, if a mooring strategy can allow the use of smaller, potentially more available lower cost vessels for hook up and tensioning, the larger Anchor Handling Vessels needed to handle large chain can be reserved for pre-laying the mooring lines only and not needed for hook up and tensioning. This aspect of planning is discussed later in this paper. The addition of unnecessary "person-hours exposed to risk" or the damage/loss of a floater due to poor mooring strategy cannot be accepted. The costs and delay impact project viability. Additionally, the potential reputational damage to the entire industry adds immeasurable risk to the success of both commercial scale floating wind farms and global emissions reduction targets. When a poor mooring strategy causes undue delays, requires expensive ships, or creates unnecessary risk, the cost of individual mooring components becomes insignificant. Considering the hook up and tensioning method holistically and logistically significantly reduces human and project risk.