Abstract

The ice resistant capacity of a FPSO and its yoke mooring system is one of the critical problems for oil field developments in the ice influenced areas of northern Bohai Bay. A model test study was conducted in the 40m×40m×2.8m Ice Tank of Helsinki University of Technology in Espoo, Finland for evaluating the maximum ice loads acting on the Suizhong 36-1 FPSO and Yoke Mooring System.

The FPSO hull, yoke mooring system, and floating ice packs were simulated for the full-scale processes in miniature. The FPSO hull and the yoke mooring jacket structure are reduced linearly in dimensions and cubic in mass, displacement, and volume, to ensure the geometric similarity. Many factors and properties are of interest when simulating ice in the ice tank. A scale ratio of 1:30 was adopted in the model test. Therefore the ice used must also be 1/30th the thickness and 1/30th the strength. ice pieces flowing, as well as jamming around the FPSO hull and the yoke mooring jacket, are modeled in the ice tank. It is very challenging to correctly reduce the ice properties of interest, thus providing an accurate simulation. The actual environment simulated in a combination of wind, current and ices is of prime concern.

This paper presents the methodology and results of the six model tests which are conducted to simulate various combinations of floating pack ice thicknesses, ice bending strengths, ice flowing speeds, FPSO headings and rotations, etc. The findings include the ice loads acting on the FPSO and Yoke Mooring Jacket at two ice flowing speeds of 0.5m/sec and 1.0 m/sec and three FPSO headings of 0, 90, 180 degrees, respectively. The FPSO model are pulled or pushed through the loose broken ice sheet to simulate the interaction between the ices and the FPSO hull. The ice load and mooring load on the yoke arms were measured by force transducers. The rotation angle of the yoke arms around the mooring jacket were also measured by angular transducers.

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