Ice Accumulation Process and Risk Analysis in Casing pipes in Bohai Sea

Under the constraints of oil/gas reserves and ocean environment, most of the offshore platforms are simple and economical in structural design in Bohai Sea, China. Ice-induced vibration responses have been measured on those platform structures in winters. However, an ice plug was observed inside the casing pipes of the JZ9-3WHPA jacket platform in winter. During the interaction of an ice sheet and the ice plug, the test data shows that the ice-induced displacement response of the casing pipe structure increases significantly, and the ice force calculation also indicates that the casing pipes have a certain safety risk. In this paper, the formation process and mechanism of the ice plug are discussed based on field observations. Manual or mechanical methods are recommended to eliminate the ice plug to ensure the safety of the casing pipes.