To make offshore operations viable in the present challenging market conditions, high operability is required. In order to achieve it, the motion response, air-gap and environmental load on the vessels should be optimized. This paper presents a study on optimizing a semi-submersible by examining a variety of aspects using different numerical tools, leading to an innovative Low Motion Semi (LMS) design. The LMS can be adopted for drilling, production, or accommodation in harsh, deep water and even arctic environments. LMS is optimized to have minimal motion characteristics and optimal station keeping capabilities using the state-of-the art technologies. Innovative technologies have been adopted to streamline four key features so as to reduce non-productive time (NPT). These include deeper pontoon submergence, use of circular hull, adoption of multi-columns and introduction of passive motion dampening air chamber. This paper presents the analysis of the innovative features of LMS using the state-of-the-art technology such as hybrid potential viscous analysis, Computational Fluid Dynamics (CFD) simulations and wave basin testing. This study also explains the practical benefits of the Passive Air Chamber, the functionality from a theoretical point of view and will show results of model tests including the Passive Air Chamber system on Low Motion Semi. The analysis and model test suggest that the LMS is able to provide very low motion characteristics, substantial air chamber effect and experience minimal environmental load.

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