MAR124 MoniMoor

Summary project

Floating wind turbines and oil and gas production systems are designed to remain on station for a prolonged period of time. They are equipped with permanent mooring systems to ensure the station keeping ability of these floaters. Performing integrity management on the mooring system is crucial, but not straightforward. Despite the fact that mooring systems have a very good safety record and undergo periodical underwater inspections, unexpected failures still happen. Fatigue is an important failure mechanism.

The MoniMoor JIP seeks to develop a framework for the mooring integrity management of floating wind turbines and production systems with the aim for reducing operation & maintenance costs, supporting lifetime extension and increasing safety.

Purpose of the project

In this project, an innovative software and framework for integrity management of the mooring system of floating offshore structures (oil & gas structures, wind turbines) will be developed with the aim of increasing safety, reducing O&M costs and support lifetime extension. This mooring integrity framework, which is part of a condition monitoring system, will be built on existing digital twin technologies improved through the coupling with an innovative hydro aero-elastic time domain numerical model. Input of this framework are in-service measurements which are obtained from dry and maintainable monitoring equipment (without costly and sensitive subsea sensors) which includes GPS positions and wave frequency motions.

Motivation

The MoniMoor project is directly related to the theme of safety and security. Despite large safety margins in the oil and gas industry mooring incidents have been occurring at high rate during the past decades. A mooring integrity framework improves the understanding of fatigue mooring loads and consequently reduces the likelihood of mooring line failures. As to the

floating wind industry, a large number of floating wind turbines are installed in the upcoming years. These floating wind turbines have, with respect to oil and gas floaters, different loading phenomena which requires specific attention, e.g. the effect of wind loads. Also, the non-linearity of synthetic mooring lines requires more attention to reduce the risk of mooring line failure incidents of floating wind turbines in the future.

Innovativeness

In depth understanding:

State of the art: mooring systems are a complex system. Their reliability is influenced by many factors, such as corrosion, fatigue, marine growth, production defects, wear and tear etc. These complexities make accurate design predictions a very complicated task and a large potential for technology improvement is present.

Our proposal: the proposed system will help identifying knowledge gaps in the mooring design life prediction for floating structures in exposed offshore dynamic application. These potential knowledge gaps are identified by comparing the measured fatigue with 1) the design fatigue, 2) the calculated fatigue based on the actual fatigue loading and the 3) motion calculated fatigue which uses the mooring line numerical model. The effect of snapping loads (floating wind turbines) and slow drift induced loads on fatigue will also be quantified. This knowledge will improve the system itself as well as mooring technology as a whole.

Scalability:

State of the art: current condition monitoring systems are based on high end sensors directly placed on the floaters. This solution is financially acceptable for energy production systems based on a small amount of floaters, but it quickly becomes too expensive when several floaters are required, such as in a floating wind farm

Our proposal: we will use an innovative aero-hydronamic model coupled with low-cost sensors to determine the condition parameters for all the floaters in a wind farm. We will carry out detailed monitoring of on just a few floaters and use this data for verification and tuning of the numerical models.

Cloud based solution:

State of the art: a digital twin system installed on floating structure typically collects the data locally as the infrastructure is not in place to stream real-time enormous amount of data to ashore. As a result existing digital twin systems process the in-service measurements locally with on-board advice,

Our proposal: floating structures nowadays are equipped with fast speed data connections to stream the data real-time to the ashore. A digital twin framework in the cloud provides the operator a web-based software for quick decision making, a historical database and data access from anywhere.

Project duration

Startdate project: 01/07/2022

End date project: 30/06/2025