The Aasta Hansteen spar in the Norwegian Sea is designed to be moored with a taut polyester rope mooring system.
The water depth at the field is 1300 meters, and due to the short installation season the most efficient hookup is with pre-installed mooring lines, which require the mooring lines to be laid down on the seabed.
DNV certification does not allow seabed contact for polyester ropes unless proven that no soil ingress and damage takes place. To be able to certify the ropes Statoil developed a test method including contact with soil, rope movement and forced water flow through the filter construction. Full scale tests were performed with actual rope and Aasta Hansteen soil, both in laboratory and at site.
This paper discusses the certification requirements and presents adequate qualification test together with results from testing.