Abstract：Deepwater semi-submersible drilling units normally move between well locations by sailing using self-propulsion, towing by tug boat, or combination of self-propulsion and towing. Comparison and analysis of these three approaches are carried out in the aspects of risk tolerance and economic efficiency using HYSY981 as an example. The results show that: self-propulsion is the most economical way of the three, combination towing is the second, but the combination towing could save a lot of time, and the time of moving the platform by self-propulsion and that by towing are almost the same to each other.
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China National Offshore Oil Corporation. HYSY981 operating manual ［M］. Beijing： China National Offshore Oil Corporation, 2015.
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China Classification Society. Guidelines for towage at sea ［S］. 2011.
