Static analysis of deepwater lazy-wave umbilical on elastic seabed

Lazy wave configuration is considered as an appropriate approach for deepwater umbilical installation due to its advantages of accommodating large vessel offsets, decoupling the vessel motions from the touchdown point of the umbilical and reducing the hang-off tension. However, the introduction of buoyancy modules system brings about the great nonlinearity of lazy wave configuration, and the configuration is also significantly affected by the change of buoyancy modules. This paper presents an analytical model to analyze the static behavior of deepwater lazy-wave umbilical on the elastic seabed. Taking the environmental loads, elastic seabed and boundary-layer phenomenon into consideration, this lazy-wave model is divided into three parts: cable segment suspended in the water, boundary-layer segment in the neighborhood of the touchdown point and touchdown segment laid on the seabed. FEM by OrcaFlex was employed to verify the accuracy of the analytical model. The results from the two methods show excellent consistency. As well, a series of sensitivity analyses are also presented to highlight the influencing parameters in lazy wave configuration. The proposed method will provide a practical reference for deepwater lazy-wave umbilical installation.