A NOVEL DESIGN OF MOBILE OFFSHORE DRILLING UNIT FOR ARCTIC CONDITIONS

Exploration of Arctic offshore for oil and gas sets extremely high requirements for Mobile Offshore Drilling Units (MODU). Arctic offshore is one of the harshest environments on the planet. Low temperatures, high winds and ice infested waters represent great challenge. Drilling units, which are optimized for severe ice loads, are vulnerable to waves when water clears from the ice. MODU's specifically designed for open water and extreme waves have poor ice resistant performance. A Novel Design of column stabilized Mobile Offshore Drilling Unit named JBF Arctic is presented in the paper. The major feature of the unit is the combination of exceptional seakeeping characteristics and excellent ice resistance. This is achieved by utilization of a dual draft concept. In open water the unit has a draft which is typical for column stabilized units. In ice the unit is submerged to a deeper draft where a cone shaped heavily reinforced upper structure receives the ice loads. This paper deals with results of extensive research including seakeeping calculations, model testing in a seakeeping tank, studies on ice loads, model testing in an ice tank, and analysis of the mooring system.