Assessing air-gap of semi-submersibles in the Northern North Sea

Abstract

Sufficient still water airgap is important both for fixed and floating platforms. What is a sufficient airgap according to the rules depends on the rule regime under which the platform is designed. All fixed platforms and floating platforms operating at one site for its design life time, platform design will follow the regulations provided by the Petroleum Safety Authority Norway. For floating platforms operating as drilling rigs, there is an opening in the regulations to design platform according to the maritime regulation. In this master thesis we will focus on a semi-submersible platform. The aim is to identify a proper set of design sea states for the platform regarding airgap assessment. We assume the platform to be operating in the Northern North Sea. NORA10 data for the years from 1957 to 2017 will be made available for the project. Transfer functions for the global motions of the platform are also available. Airgap values will be presented.